A high-wear-resistant and high-accident-resistant forged semi-steel billet roll and its forging method

Abstract

This invention relates to a forged semi-steel billet roll with high wear resistance and high accident resistance, and its forging method. Belonging to the field of forging technology, it solves the problem of poor matching between wear resistance and toughness in existing billet rolls, which cannot simultaneously achieve good wear resistance and toughness. This invention provides a forging method for a semi-steel billet roll, which involves heat-treating, pre-drawing, upsetting, elongating, blanking, and then heating and holding the roll at a specific temperature to obtain the finished semi-steel billet roll. The forged semi-steel billet roll prepared by this method has a hardness of 35–60 HSD; a room temperature yield strength of 480–800 MPa; a tensile strength of 800–1300 MPa; good matching between wear resistance and toughness; significantly improved accident resistance; a slower decrease in strength at high temperatures; and a hardness difference of ≤3HS within a 200mm surface area, making it suitable for creating deep grooves.

Description

Technical Field

[0001] This invention relates to the field of forging technology, and in particular to a forging semi-steel billet roll with high wear resistance and high accident resistance, and its forging method. Background Technology

[0002] The roughing roll is the first roll in a steel rolling production line, operating under harsh conditions and prone to hot cracking. Therefore, the roll surface must possess sufficient thermal strength and high wear resistance, heat resistance, and impact resistance. Currently, the materials used for hot-rolled roughing rolls in China include forged steel 60CrMnMo, 60CrNiMo, ductile iron, 75CrNiMo cast steel, and cast semi-steel. While forged steel 60CrMnMo and 60CrNiMo hot-rolled work rolls have high toughness, their wear resistance is poor. The working layer is predominantly pearlitic, making them highly susceptible to cracking. High-temperature strength decreases significantly, while plasticity increases, leading to plastic deformation and wrinkling of the roll surface. Ductile iron has poor wear resistance; cast steel and cast semi-steel have very poor toughness, making roll breakage accidents common.

[0003] Therefore, it is necessary to develop a roughing roll with good wear resistance, strength, plasticity, toughness matching, and high accident resistance. Summary of the Invention

[0004] Based on the above analysis, the present invention aims to provide a forged semi-steel billet roll with high wear resistance and high accident resistance, and its forging method, in order to solve the problem that the existing billet rolls have poor matching degree of wear resistance, strength, plasticity and toughness, and cannot have good wear resistance and strength, plasticity and toughness at the same time.

[0005] This invention provides a forging method for semi-steel billet rolls, specifically including the following steps:

[0006] S1 First Heat: The steel ingot is quickly fed into the furnace and heat-treated according to the preset stepped heating curve; after the heat treatment is completed, it is taken out of the furnace, chamfered, clamped, and the bottom of the ingot and the clamp handle are cut off by gas cutting to discard the material.

[0007] S2 Second Heat: After heating and holding the S1 treated steel ingot at a temperature of T start ±10℃, the holding time is 30-60 minutes per 100mm of the average diameter of the water riser of the steel ingot. After taking it out of the furnace, use upper and lower V-shaped anvils to pre-draw it to the required diameter according to the pre-drawing ratio of 1.0-1.5.

[0008] S3 Third Heat: After heating and holding the S2 treated steel ingot at a temperature of T start ±10℃, the holding time is 2 to 5 hours per 100mm of pre-drawn diameter. After taking it out of the furnace, it is upset to the required height according to the upsetting ratio of 1.5 to 2.0.

[0009] S4 Fourth Heat: After heating and holding the S3 treated steel ingot at a temperature of T start ±10℃, the holding time is 30-60 minutes per 100mm of upsetting height. After taking it out of the furnace, use upper and lower V-shaped anvils to draw it to the required diameter according to the KD drawing ratio of 1.5-2.5.

[0010] S5 Fifth Fire: After heating and holding the S4 treated steel ingot at a temperature of T start ±10℃, the holding time is 2-5 hours per 100mm of drawing diameter. After exiting the furnace, continue to draw the blank to the large circle diameter of the blank using KD. Cut the blank at both ends according to the process requirements. Use KD to pinch out the water riser roll neck to obtain the semi-finished blank roll.

[0011] S6 Sixth Fire: After heating and holding the semi-finished blank roll at a temperature of T start ±10℃, the holding time is 30-60 minutes for every 100mm of the diameter of the roll neck after the first fire. After exiting the furnace, KD stretches the roll necks at both ends to the roll neck size of the blank drawing, and then rounds them to produce the finished blank roll.

[0012] Where Tinitial is the initial forging temperature, ranging from 1100 to 1200℃.

[0013] Specifically, the steel ingot is a semi-steel casting steel ingot, and its composition by mass percentage is: C 1.0-1.6%, Si 0.2-0.7%, Mn 0.4-1.0%, Cr 1.0-2.0%, Ni 0.1-1.0%, Mo 0.2-0.8%, P and S ≤0.02%, with the remainder being iron and other impurity elements; and among the impurity elements, Cu+Pb+Sb+As+Bi+Sn+Zn <0.2%.

[0014] Specifically, the stepped heating curve mentioned in step S1 is as follows:

[0015] Preheating stage: The steel ingot is heated to Tpre and held at that temperature, where Tpre is 750–850°C;

[0016] Homogenization diffusion stage: Heat the steel ingot to Texpansion ±10℃ and hold it at that temperature. The heating rate is ≤50℃ / h, where Texpansion = Tinitial +30℃.

[0017] Initial forging stage: The steel ingot is slowly cooled to Tinitial ±10℃ and held at that temperature, with a cooling rate ≤50℃ / h.

[0018] Furthermore, the holding time for the preheating stage is h1, the holding time for the homogenization and diffusion stage is h2, and the holding time for the initial forging stage is h3; h1, h2, and h3 are determined according to the diameter of the steel ingot, with h1 held for 40 to 80 minutes per 100 mm, h2 held for 2 to 5 hours per 100 mm, and h3 held for 1 to 2 hours per 100 mm.

[0019] Specifically, the final forging temperature for each step is ≥850℃.

[0020] Specifically, the specific operation and parameters of step S2 are as follows: the pressing amount is ≥ 20% of the billet height, 90° flip, and pressing down one pass with the anvil offset.

[0021] Specifically, the specific operation and parameters of step S4 are as follows: the reduction amount is ≥ 20% of the billet height, 90° flip, and odd-even anvil arrangement.

[0022] Specifically, after obtaining the finished billet roll in step S6, the billet roll is cooled to 600±10℃ before being placed into the forging furnace. The purpose of cooling to 600±10℃ before placing it into the forging furnace is to accelerate the cooling rate and avoid the precipitation of network carbides or excessively high precipitation temperature.

[0023] Specifically, the total forging ratio of the forging method is ≥3.

[0024] This invention provides a forged semi-steel blanking roll with high wear resistance and high accident resistance. The blanking roll is made by the forging method described above. The hardness of the forged semi-steel blanking roll is 35-60HSD, and the large amount of free carbides improves the wear resistance. The room temperature yield strength reaches 480-800MPa, and the tensile strength reaches 800-1300MPa. The hardness difference within 200mm of the surface is ≤3HS, which is suitable for making deep hole grooves.

[0025] At high temperatures, the strength index decreases more slowly, the thermal strength is higher, the plasticity index changes little, and the softening phenomenon is less pronounced. It is less prone to plastic deformation during high-temperature rolling, ensuring both strength and toughness, and improving the phenomena of wrinkles, protrusions, and steel sticking within the roll grooves. Furthermore, because the semi-steel roll is composed of a uniform pearlitic matrix and carbides from the surface to the interior, the hardness difference within a 200mm range on the surface is ≤3HS, making it particularly suitable for section steel rolls with deep grooves.

[0026] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0027] 1. This invention provides a forging method specifically for forging semi-steel billet rolls, which has a good effect on improving segregation of steel ingots and preventing surface and core cracks.

[0028] Traditional roughing rolls are made of materials such as forged steel 60CrMnMo, 60CrNiMo, ductile iron, 75CrNiMo cast steel, and cast semi-steel. Although forged steel 60CrMnMo and 60CrNiMo hot-rolled work rolls have high toughness, they have poor wear resistance. The working layer is mainly composed of pearlite, which makes them prone to cracking. Their high-temperature strength index decreases significantly, while their plasticity index increases, leading to plastic deformation and wrinkling of the roll surface. Ductile iron has poor wear resistance. Cast steel and cast semi-steel have very poor toughness and are prone to roll breakage accidents.

[0029] This invention aims to provide a forged semi-steel billet roll with high wear resistance and high accident resistance. Semi-steel material is selected as the raw material. Semi-steel material has good comprehensive properties, with good strength and toughness, high and relatively uniform hardness, and has the potential to be used to make rolls. However, semi-steel material has a high carbon content, serious ingot segregation, and serious original shrinkage porosity. Conventional forging methods sacrifice the reduction per pass in order to control surface cracks, resulting in a very low product qualification rate, poor product performance stability, and failure to fully utilize the material's performance.

[0030] After the steel ingot arrives, it is heated using a stepped heating curve to prevent cracks from forming on the surface and in the core of the steel ingot due to structural stress and temperature stress. At the same time, high-temperature diffusion improves element segregation. In particular, the special stepped heating curve provided by this invention has a better effect.

[0031] After the steel ingot is heated and taken out of the furnace for the first time, a pre-drawing process is set up. Pre-drawing breaks the cast structure on the surface of the steel ingot through a small deformation, reduces the generation of upsetting cracks, and prepares the structure for subsequent high-temperature diffusion.

[0032] Furthermore, strictly control the final forging temperature of each heat treatment to ≥850℃, and stop forging before carbides precipitate on the surface to avoid forging cracks caused by network carbides.

[0033] This forging method increases the holding time before forging in both the upsetting and KD compaction stages. The purpose is to achieve high-temperature diffusion, reduce element segregation, homogenize the microstructure, and improve the toughness and strength of the product through long-term heat preservation.

[0034] The forging method provided by this invention can effectively compact defects in the core of steel ingots, refine grains, and improve product toughness and strength.

[0035] 2. The forging semi-steel billet roll provided by this invention has good wear resistance and a high degree of matching with strength, plasticity and toughness.

[0036] The selected forged semi-steel material has a high carbon content and contains a large amount of free carbides in its structure, resulting in better wear resistance. Its room temperature yield strength reaches 480-800 MPa, and its tensile strength reaches 800-1300 MPa. It also has high thermal strength and is not prone to plastic deformation during high-temperature rolling, ensuring strength while taking into account plasticity and toughness, and improving the phenomena of wrinkles, protrusions, and steel sticking in the roll grooves.

[0037] The forged semi-steel billet roll provided by this invention has a microstructure composed of a uniform pearlite matrix and carbides from the surface to the interior. The hardness difference within a 200mm range on the surface is ≤3HS, and there is almost no hardness drop within the working layer. It is especially suitable for preparing profile rolls with deep grooves.

[0038] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained from what is particularly pointed out in the description and drawings. Attached Figure Description

[0039] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0040] Figure 1 This is a schematic diagram of a stepped heating curve;

[0041] Figure 2 This is a blanking process diagram of the semi-steel billet roll in Example 1;

[0042] Figure 3 This is a process diagram showing the heating curve of the first fire in Example 1;

[0043] Figure 4 This is a diagram showing the blanking process of the semi-steel billet rolling mill in Example 1;

[0044] Figure 5 This is a blanking process diagram of the semi-steel billet roll in Example 2;

[0045] Figure 6 This is a process diagram showing the heating curve of the first fire in Example 2;

[0046] Figure 7 This is a diagram showing the blanking process of the semi-steel billet rolling mill in Example 2;

[0047] Figure 8 This is a blanking process diagram of the semi-steel billet roll in Example 3;

[0048] Figure 9 This is a process diagram showing the heating curve of the first fire in Example 3;

[0049] Figure 10 This is a diagram showing the blanking process of the semi-steel billet roll in Example 3. Detailed Implementation

[0050] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of this application and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0051] Traditional roughing rolls are made of materials such as forged steel 60CrMnMo, 60CrNiMo, ductile iron, 75CrNiMo cast steel, and cast semi-steel. Although forged steel 60CrMnMo and 60CrNiMo hot-rolled work rolls have high toughness, they have poor wear resistance. The working layer is mainly composed of pearlite, which makes them prone to cracking. Their high-temperature strength index decreases significantly, while their plasticity index increases, leading to plastic deformation and wrinkling of the roll surface. Ductile iron has poor wear resistance. Cast steel and cast semi-steel have very poor toughness and are prone to roll breakage accidents.

[0052] This invention aims to provide a forged semi-steel roll with high wear resistance and high accident resistance. Semi-steel is selected as the raw material because it possesses good comprehensive properties, including good strength and toughness, and relatively uniform hardness, making it a potential material for rolling mill rolls. However, semi-steel has a high carbon content, resulting in severe ingot segregation and significant initial shrinkage cavities and porosity. Conventional forging methods sacrifice per pass reduction to control surface cracks, leading to extremely low product yield, poor product performance stability, and failure to fully utilize the material's properties. Therefore, it is necessary to develop a forging method for semi-steel rolls with good process stability.

[0053] The forging method provided by this invention employs a stepped heating curve for the initial heating. The holding time is increased before the upsetting and KD compaction heating processes to prevent cracks from forming on the surface and in the core of the ingot due to structural and thermal stresses. Simultaneously, high-temperature diffusion improves element segregation. After the ingot is first heated and removed from the furnace, a pre-drawing process is implemented to reduce upsetting cracks. The KD compaction drawing process uses an odd-even pass anvil arrangement, with a single pass reduction of ≥20%. Furthermore, the anvil type is rationally selected, and the total number of heating processes and the deformation per process are rationally arranged to avoid core cracks. The final product exhibits good wear resistance and a high degree of matching between strength, plasticity, and toughness.

[0054] This invention provides a forging method for semi-steel billet rolls, specifically including the following steps:

[0055] S1 First Heat: The steel ingot is quickly fed into the furnace and heat-treated according to the preset stepped heating curve; after the heat treatment is completed, it is taken out of the furnace, chamfered, clamped, and the bottom of the ingot and the clamp handle are cut off by gas cutting to discard the material.

[0056] S2 Second Heat: After heating and holding the S1 treated steel ingot at a temperature of T start ±10℃, the holding time is 30-60 minutes per 100mm of the average diameter of the water riser of the steel ingot. After taking it out of the furnace, use upper and lower V-shaped anvils to pre-draw it to the required diameter according to the pre-drawing ratio of 1.0-1.5.

[0057] The purpose of this step is to break up the as-cast structure on the surface of the steel ingot through a certain amount of deformation, thereby reducing the occurrence of upsetting cracks. On the other hand, pre-drawing can shorten the interdendritic distance and improve the subsequent high-temperature diffusion effect;

[0058] S3 Third Heat: After heating and holding the S2 treated steel ingot at a temperature of T start ±10℃, the holding time is 2 to 5 hours per 100mm of pre-drawn diameter. After taking it out of the furnace, it is upset to the required height according to the upsetting ratio of 1.5 to 2.0.

[0059] After the first pre-drawing (i.e., the second heat treatment), the as-cast microstructure of the steel ingot is improved to a certain extent, and the dendritic structure becomes denser. This step extends the holding time at the initial forging temperature. The purpose is to achieve high-temperature diffusion homogenization through prolonged high-temperature holding, reducing microscopic element segregation between dendrites and improving forging performance. The longer the high-temperature diffusion time, the better the diffusion effect. However, after diffusion reaches a certain point, the element concentration gradient gradually decreases. At this point, increasing the diffusion time results in slower homogenization, wasting energy and even leading to coarse grains. Therefore, the holding time must be neither insufficient nor too long.

[0060] S4 Fourth Heat: After heating and holding the S3 treated steel ingot at a temperature of T start ±10℃, the holding time is 30-60 minutes per 100mm of upsetting height. After taking it out of the furnace, use upper and lower V-shaped anvils to draw it to the required diameter according to the KD drawing ratio of 2.0-2.5.

[0061] After the previous upsetting (third upsetting), some axial defects have been initially improved. At the same time, upsetting increased the diameter of the billet, providing sufficient elongation for this upsetting. The elongation for this upsetting is set to no more than 2.5. Insufficient elongation will make it difficult to compact the original defects in the core, while excessive elongation will cause cracks in the core. The anvil placement method and the amount of reduction per pass are also specified to ensure complete compaction of the core defects.

[0062] S5 Fifth Fire: After heating and holding the S4 treated steel ingot at a temperature of T start ±10℃, the holding time is 2-5 hours per 100mm of drawing diameter. After exiting the furnace, continue to draw the blank to the large circle diameter of the blank using KD. Cut the blank at both ends according to the process requirements. Use KD to pinch out the water riser roll neck to obtain the semi-finished blank roll.

[0063] Following the previous forging process, the KD drawing continues to the final size of the large circle. At the same time, the holding time at the initial forging temperature is extended in this forging process to achieve high-temperature diffusion homogenization, reduce micro-segregation of elements between dendrites, and improve forging performance.

[0064] S6 Sixth Fire: After heating and holding the semi-finished blank roll at a temperature of T start ±10℃, the holding time is 30-60 minutes for every 100mm of the diameter of the roll neck after the first fire. After exiting the furnace, KD stretches the roll necks at both ends to the roll neck size of the blank drawing, and then rounds them to produce the finished blank roll.

[0065] The special feature of this firing process is that after the billet exits the furnace, the large circle is not allowed to deform further to avoid tensile stress on the core caused by small deformations, which could lead to core cracks. At the same time, the roller necks at both ends are drawn out into finished products using KD anvils and shovels. The purpose is to ensure that the core is under biaxial or triaxial compressive stress to prevent core cracks.

[0066] Among them, Tinitial is the initial forging temperature, which ranges from 1150 to 1200℃. The selection of the initial forging temperature is closely related to the material and is generally 100 to 150℃ lower than the solidus temperature of the material.

[0067] Specifically, this forging method controls surface cracks while achieving sufficient compaction of core defects in brittle and easily fractured materials, significantly improving the product qualification rate to over 90%. Forged semi-steel blanking rolls produced using this method exhibit significantly better wear resistance and accident resistance than traditional blanking roll materials, making them more suitable for blanking rolls with deep grooves.

[0068] Specifically, the steel ingot is a semi-steel casting steel ingot, and its composition by mass percentage is: C 1.0-1.6%, Si 0.2-0.7%, Mn 0.4-1.0%, Cr 1.0-2.0%, Ni 0.1-1.0%, Mo 0.2-0.8%, P and S ≤0.02%, with the remainder being iron and other impurity elements; and among the impurity elements, Cu+Pb+Sb+As+Bi+Sn+Zn <0.2%.

[0069] Specifically, the stepped heating curve mentioned in step S1 is as follows:

[0070] Preheating stage: The steel ingot is heated to Tpre and held at that temperature, where Tpre is 750–850°C;

[0071] Homogenization diffusion stage: Heat the steel ingot to Texpansion ±10℃ and hold it at that temperature. The heating rate is ≤50℃ / h, where Texpansion = Tinitial +30℃.

[0072] Initial forging stage: The steel ingot is slowly cooled to Tinitial ±10℃ and held at that temperature, with a cooling rate ≤50℃ / h.

[0073] Furthermore, the holding time for the preheating stage is h1, the holding time for the homogenization and diffusion stage is h2, and the holding time for the initial forging stage is h3. h1, h2, and h3 are determined according to the diameter of the steel ingot. h1 is held for 40 to 80 minutes per 100 mm, h2 is held for 2 to 5 hours per 100 mm, and h3 is held for 1 to 2 hours per 100 mm.

[0074] The preheating stage serves to set the temperature near the phase transformation temperature to ensure uniform internal and external temperature and microstructure, preventing cracks from forming on the surface and in the core of the steel ingot due to microstructural and thermal stresses.

[0075] Homogenization diffusion stage: A higher diffusion temperature is set to achieve a better diffusion effect in a shorter time. High-temperature diffusion improves element segregation.

[0076] Initial forging stage: In order to avoid excessive temperature rise in the core due to deformation heat effect, resulting in overheating and burning, the temperature is reduced to a suitable initial forging temperature before forging, and then held at that temperature for a period of time before forging.

[0077] Specifically, the specific operation of pressing the jaws in step S1 is as follows: press the jaws 100mm from the riser end of the ingot body, and determine the jaw size according to the inner diameter of the matching upsetting stencil. Cut the bottom of the ingot and discard the jaws.

[0078] Specifically, the final forging temperature for each step is ≥850℃.

[0079] Specifically, the specific operation and parameters of step S2 are as follows: the pressing amount is ≥ 20% of the billet height, 90° flip, and pressing down one pass with the anvil offset.

[0080] Specifically, the specific operation and parameters of step S4 are as follows: the reduction amount is ≥ 20% of the billet height, 90° flip, and odd-even anvil arrangement.

[0081] Specifically, after obtaining the finished billet roll in step S6, it is placed in air cooling and cooled to 600±10℃ before being put into the forging furnace. The purpose of this is to accelerate the cooling rate, avoid the precipitation of network carbides or excessively high precipitation temperature, reduce the precipitation of network carbides, and thus avoid cracking caused by network carbides.

[0082] Specifically, the total forging ratio of the forging method is ≥3 to achieve the effect of fully compacting the core.

[0083] Specifically, this forging method controls surface cracks while achieving sufficient compaction of core defects in brittle and easily fractured materials, significantly improving product qualification rate. Forged semi-steel roughing rolls produced using this method have a microstructure composed of a uniform pearlitic matrix and carbides from the surface to the interior, with a hardness difference of ≤3HS within a 200mm surface area, making them more suitable for roughing rolls with deep grooves.

[0084] This invention provides a forged semi-steel billet roll with high wear resistance and high accident resistance. The billet roll is made by the forging method and its wear resistance and accident resistance are significantly better than those of traditional billet roll materials.

[0085] Specifically, the microstructure of the forged semi-steel billet roll consists of a pearlite matrix and a large amount of free carbides. Because the free carbide content is 15-25% (high), its wear resistance is higher than that of ordinary forged steel and ductile iron rolls. Furthermore, after processing using the forging method proposed in this invention, its strength is significantly improved compared to cast steel rolls. The presence of free carbides also results in a higher high-temperature hardness for the semi-steel roll compared to cast steel rolls, preventing plastic flow in the matrix and reducing wrinkles on the roll surface.

[0086] Furthermore, the surface hardness difference of the forged semi-steel billet roll within 200mm is ≤3HS, making it particularly suitable for section steel rolls with deep grooves.

[0087] According to the standard requirements, the defect equivalent of the working layer should be ≤Ф2, the defect equivalent of other areas should be ≤Ф6, and the defect wave should be ≤50%, which meets the flaw detection standard.

[0088] Example 1

[0089] The selected material has the following chemical composition: C 1.6%, Si 0.5%, Mn 0.6%, Cr 1.5%, Ni 0.5%, Mo 0.5%, P and S 0.005%, with remaining impurities Cu+Pb+Sb+As+Bi+Sn+Zn < 0.2%. Based on the blank size (below...) Figure 2 Select a suitable steel ingot. In this embodiment, a 66T steel ingot is used for forging. The sprue size is 1615mm, the riser size is 1838mm, and the average size is 1726.5mm.

[0090] First firing: Press after the ingot arrives. Figure 3 The curve is executed for pre-forging heating and heat preservation. After exiting the furnace, the ingot is chamfered, and the 800×1000mm pliers are pressed into the ingot bottom and pliers handle 100mm from the riser end of the ingot.

[0091] Second firing: Heating furnace at 1150±10℃, holding for 15h, KD pre-drawing to Φ1550mm, pressing down by 20% of billet height, 90° flipping, pressing down once with an anvil, pre-drawing ratio is 1.24.

[0092] Third heating cycle: Heating furnace at 1150±10℃, holding for 40 hours, then upsetting to H=1800mm after exiting the furnace, with an upsetting ratio of 1.9.

[0093] Fourth firing: Heating furnace at 1150±10℃, holding for 18 hours, KD drawing six times to Φ1450mm, pressing down by 20% of billet height, 90° flipping, odd and even anvil arrangement, drawing ratio of 2.1.

[0094] Fifth firing: Heating furnace 1150±10℃, holding for 40 hours, then drawing the KD (knives) to Φ1330mm after firing. Figure 4 Cut the material and cut the roller necks at both ends to the required length, with a diameter of Φ900mm.

[0095] Sixth firing: Heating furnace at 1150±10℃, holding for 6 hours, KD drawing with both ends of the roller necks extended after exiting the furnace, rounding to the diameter required by the blank drawing, and gas cutting off the excess material at both ends to produce the finished product.

[0096] The surface was almost free of cracks during the forging process, the production process was smooth, and the finished product was produced in six forging passes.

[0097] After the roughing roll cools to 600±10℃, it is placed in the forging furnace and subjected to spray quenching and tempering heat treatment. The hardness after this treatment is 46-50 HSD. At room temperature, the yield strength is 585 MPa, tensile strength is 1101 MPa, elongation is 5%, reduction of area is 5%, and impact resistance is 7J. The hardness at 200 mm from the surface is 45-48 HSD, with a hardness decrease of ≤3 HSD.

[0098] At 500℃, the yield strength is 322MPa, the tensile strength is 549MPa, the elongation is 55%, the reduction of area is 22%, and the impact performance is 17J. The defect equivalent of the working layer is ≤Ф1, the defect equivalent of other areas is ≤Ф4, the bottom wave is 100%, and the defect wave is <10%, which meets the requirements of the flaw detection standard.

[0099] Example 2

[0100] The selected material has the following chemical composition: C 1.4%, Si 0.55%, Mn 0.55%, Cr 1.45%, Ni 0.53%, Mo 0.56%, P and S 0.004%, and the remaining impurity elements Cu+Pb+Sb+As+Bi+Sn+Zn < 0.2%. This is based on the blank size. Figure 5 Select a suitable steel ingot. In this embodiment, a 70T steel ingot is used for forging. The sprue size is 1668mm, the riser size is 1952mm, and the average size is 1810mm.

[0101] First firing: After the ingot arrives, follow the special curve. Figure 6 Perform pre-forging heating and heat preservation. After exiting the furnace, beveling is done. Starting 100mm from the riser end of the ingot, the clamp jaws are pressed with Φ1000×1000. The bottom of the ingot and the clamp handle are cut with gas to remove waste material.

[0102] Second firing: Heating furnace at 1170±10℃, holding for 18h, KD pre-drawing to Φ1600mm, pressing down by 20% of billet height, 90° flipping, pressing down once with an anvil, pre-drawing ratio is 1.28.

[0103] Third heating cycle: Heating furnace at 1170±10℃, holding for 45 hours, then upsetting to H=1800mm after exiting the furnace, with an upsetting ratio of 1.9.

[0104] Fourth firing: Heating furnace at 1170±10℃, holding for 18 hours, KD drawing six times to Φ1480mm, pressing down by 20% of billet height, 90° flipping, odd and even anvil arrangement, drawing ratio of 2.3.

[0105] Fifth firing: Heating furnace 1170±10℃, holding for 45 hours, then drawing the KD (knives) to Φ1350mm after firing. Figure 7 Cut the material and pinch out the roller necks at both ends to the required diameter Φ900mm.

[0106] Sixth firing: Heating furnace at 1170±10℃, holding for 7.5h, KD drawing at both ends of the roller neck after exiting the furnace, rounding to the diameter required by the blank drawing, and cutting off the excess material at both ends to produce the finished product.

[0107] The surface was almost free of cracks during the forging process, the production process was smooth, and the finished product was produced in six forging passes.

[0108] After the roughing roll cools to 600±10℃, it is placed in the forging furnace and subjected to spray quenching and tempering heat treatment. The hardness after this treatment is 45~48HSD. At room temperature, the yield strength is 568MPa, tensile strength is 1100MPa, elongation is 6.5%, reduction of area is 6%, and impact resistance is 7J. The hardness at 200mm from the surface is 43-46HSD, with a hardness decrease of ≤3HSD.

[0109] At 500℃, the yield strength is 320MPa, the tensile strength is 545MPa, the elongation is 57%, the reduction of area is 23%, and the impact performance is 18J. The defect equivalent of the working layer is ≤Ф1~2, the defect equivalent of other areas is ≤Ф4~5, the bottom wave is 90~100%, and the defect wave is <30%, which meets the requirements of the flaw detection standard.

[0110] Example 3

[0111] The selected material has the following chemical composition: C 1.3%, Si 0.65%, Mn 0.58%, Cr 1.5%, Ni 0.55%, Mo 0.56%, P and S 0.004%, and the remaining impurity elements Cu+Pb+Sb+As+Bi+Sn+Zn < 0.2%. This is based on the blank size. Figure 8 Select a suitable steel ingot. In this embodiment, a 74T steel ingot is used for forging. The sprue size is 1760mm, the riser size is 2058mm, and the average size is 1909mm.

[0112] First firing: After the ingot arrives, follow the special curve. Figure 9 Perform pre-forging heating and heat preservation. After exiting the furnace, beveling is done. Starting 100mm from the riser end of the ingot, the clamp jaws are pressed with Φ1000×1000. The bottom of the ingot and the clamp handle are cut with gas to remove waste material.

[0113] Second firing: Heating furnace at 1180±10℃, holding for 19h, KD pre-drawing to Φ1650mm, pressing down by 20% of billet height, 90° flipping, pressing down once with an anvil, pre-drawing ratio of 1.3.

[0114] Third heating cycle: Heating furnace at 1180±10℃, holding for 45 hours, then upsetting to H=1850mm after exiting the furnace, with an upsetting ratio of 1.85.

[0115] Fourth firing: Heating furnace at 1180±10℃, holding for 18h, KD drawing six times to Φ1500mm after exiting the furnace, pressing down by 20% of the billet height, 90° flipping, odd and even anvil arrangement, drawing ratio of 2.4.

[0116] Fifth firing: Heating furnace 1180±10℃, holding for 45 hours, then drawing the KD (knives) to Φ1370mm after firing. Figure 10 Cut the material and pinch out the roller necks at both ends to the required diameter Φ900mm.

[0117] Sixth firing: Heating furnace at 1180±10℃, holding for 9 hours, KD drawing with both ends of the roller necks extended after exiting the furnace, rounding to the diameter required by the blank drawing, and gas cutting off the excess material at both ends to produce the finished product.

[0118] The surface was almost free of cracks during the forging process, the production process was smooth, and the finished product was produced in six forging passes.

[0119] After the roughing roll cools to 600±10℃, it is placed in the forging furnace and subjected to quenching and tempering heat treatment. The hardness after this treatment is 43~47HSD. At room temperature, the yield strength is 547MPa, tensile strength is 1044MPa, elongation is 9%, reduction of area is 10%, and impact resistance is 8J. The hardness at 200mm from the surface is 41-45HSD, with a hardness decrease of ≤3HSD.

[0120] At 500℃, the yield strength is 335MPa, the tensile strength is 540MPa, the elongation is 57%, the reduction of area is 23%, and the impact performance is 18J. The defect equivalent of the working layer is ≤Ф2, the defect equivalent of other areas is ≤Ф5, the bottom wave is >80%, and the defect wave is <30%, which meets the requirements of the flaw detection standard.

[0121] Comparative Example 1

[0122] The selected material has the following chemical composition: C 1.6%, Si 0.5%, Mn 0.6%, Cr 1.5%, Ni 0.5%, Mo 0.5%, P and S 0.005%, and the remaining impurity elements Cu+Pb+Sb+As+Bi+Sn+Zn < 0.2%. A suitable steel ingot was selected based on the blank size (same as in Example 1). This comparative example uses a 66T steel ingot forging, with a sprue size of 1615mm, a riser size of 1838mm, and an average size of 1726.5mm.

[0123] First firing: After the ingot arrives, perform pre-forging heating and heat preservation according to the special curve (same as Example 1). After exiting the furnace, bevel the edges, press the 800×1000mm jaws on the riser end of the ingot, and cut the bottom of the ingot and discard the jaws.

[0124] Second heating: Heating furnace at 1180±10℃, holding for 40 hours, then upsetting to H=1800mm after exiting the furnace, with an upsetting ratio of 1.53.

[0125] Third firing: Heating furnace at 1180±10℃, holding for 18h, KD drawing six times to Φ1450mm after exiting the furnace, pressing down by 20% of the billet height, 90° flipping, odd and even anvil arrangement, drawing ratio of 2.1.

[0126] Fourth firing: Heating furnace at 1180±10℃, holding for 10 hours, removing from the furnace, flattening the upper and lower V-shaped anvils, lengthening the roller body to Φ1370mm, and pinching the roller necks at both ends to Φ900mm.

[0127] Fifth fire: Heat the furnace to 1180±10℃, keep it at that temperature for 8 hours, then remove it from the furnace and flatten it with a V-shaped anvil. Lengthen the roller necks at both ends to the diameter required by the blank drawing, and then cut off the excess material at both ends to get the finished product.

[0128] The forging process resulted in minor surface cracks, but production proceeded smoothly, with the finished product emerging from the fifth forging pass. The ultrasonic testing roller showed no bottom echo, and the defect rate was >50%, failing to meet the flaw detection standards.

[0129] Comparative Example 2

[0130] The selected material has the following chemical composition: C 1.6%, Si 0.5%, Mn 0.6%, Cr 1.5%, Ni 0.5%, Mo 0.5%, P and S 0.005%, and the remaining impurity elements Cu+Pb+Sb+As+Bi+Sn+Zn < 0.2%. A suitable steel ingot was selected based on the blank size (same as in Example 1). This comparative example uses a 66T steel ingot forging, with a sprue size of 1615mm, a riser size of 1838mm, and an average size of 1726.5mm.

[0131] First firing: Heating furnace 1150±10℃, chamfering after exiting the furnace, pressing the 800×1000mm jaws on the riser end of the steel ingot, and cutting the bottom of the ingot and discarding the cleaver handle with gas.

[0132] Second upsetting: Heating furnace at 1150±10℃, holding for 40 hours, then upsetting to H=1800mm after exiting the furnace, with an upsetting ratio of 1.53.

[0133] Third firing: Heating furnace at 1150±10℃, holding for 18 hours, KD drawing six times to Φ1450mm after exiting the furnace, pressing down by 20% of the billet height, 90° flipping, odd and even anvil arrangement, drawing ratio of 2.1.

[0134] Fourth firing: Heat the furnace to 1150±10℃, keep warm for 10 hours, remove from the furnace, flatten the top and pull the bottom V-shaped anvil to lengthen the roller body to Φ1370mm, and pinch the roller necks at both ends to Φ1000mm.

[0135] Fifth fire: Heat the furnace to 1150±10℃, keep it at that temperature for 10 hours, then remove it from the furnace and flatten it with a V-shaped anvil. Lengthen the roller necks at both ends to the diameter required by the blank drawing, and then cut off the excess material at both ends to get the finished product.

[0136] The forging process resulted in minor surface cracks, but production proceeded smoothly, with the finished product emerging after five passes. The ultrasonic testing roller body exhibited internal cracks, significant attenuation of the bottom wave (less than 10%), and a defective wave rate of 70-80%, failing to meet the flaw detection standards.

[0137] Microcracks appeared on the surface of both Comparative Example 1 and Comparative Example 2 during the forging process. This was because the pre-drawing process was not performed, and the surface cast structure was not broken up, which led to surface cracks during the large deformation upsetting.

[0138] The reason why the heart of Comparative Example 1 was found to be bottomless during ultrasonic testing was that Comparative Example 1 did not perform the pre-drawing process, resulting in poor high-temperature diffusion. At the same time, the initial forging temperature was set too high, causing the heart to overheat and the heart defects to be magnified.

[0139] Comparative Example 2 shows cracks in the heart cavity during ultrasonic testing, with large attenuation of the bottom wave and high defect wave height. This is because Comparative Example 2 did not perform the special curve and pre-pull-out process, resulting in high stress in the heart cavity, poor diffusion effect, and insufficient compaction of the heart cavity defect.

[0140] There are differences in performance among the various embodiments. The flaw detection quality of Embodiment 1 is the best because the segregation of the steel ingot is well controlled and the core defects are fully compacted.

[0141] The flaw detection quality of Example 3 is slightly worse than that of Example 1 because the steel ingot used is larger in tonnage, the original segregation of the steel ingot is more serious, the requirements for initial forging temperature control are more stringent, and higher requirements are placed on high-temperature diffusion temperature and time.

[0142] In summary, the semi-steel billet roll forged by this invention has a hardness of 35-60 HSD, a room temperature yield strength of 480-800 MPa, a tensile strength of 800-1300 MPa, an elongation of ≥6.5%, a reduction of area of ​​≥6%, and an impact performance of ≥7J.

[0143] Yield strength at 500℃ ≥320MPa, tensile strength ≥540MPa, elongation ≥57%, reduction of area ≥23%, impact performance ≥18J;

[0144] The working layer defect equivalent is ≤Ф2, the other areas defect equivalent is ≤Ф5, the bottom wave is >50%, the defect wave is <50%, which meets the requirements of the flaw detection standard; the hardness difference within 200mm of the surface is ≤3HS.

[0145] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A forging method for a semi-steel billet roll, characterized in that, Specifically, the following steps are included: S1 First Heat: The steel ingot is quickly fed into the furnace and heat-treated according to the preset stepped heating curve; after the heat treatment is completed, it is taken out of the furnace, chamfered, clamped, and the bottom of the ingot and the clamp handle are cut off by gas cutting to discard the material. S2 Second Heat: After heating and holding the S1 treated steel ingot at a temperature of T start ±10℃, the holding time is 30-60 minutes per 100mm of the average diameter of the water riser of the steel ingot. After taking it out of the furnace, use upper and lower V-shaped anvils to pre-draw it to the required diameter according to the pre-drawing ratio of 1.0-1.

5. S3 Third Heat: After heating and holding the S2 treated steel ingot at a temperature of T start ±10℃, the holding time is 2 to 5 hours per 100mm of pre-drawn diameter. After taking it out of the furnace, it is upset to the required height according to the upsetting ratio of 1.5 to 2.

0. S4 Fourth Heat: After heating and holding the S3 treated steel ingot at a temperature of T start ±10℃, the holding time is 30-60 minutes per 100mm of upsetting height. After taking it out of the furnace, use upper and lower V-shaped anvils to draw it to the required diameter according to the KD drawing ratio of 1.5-2.

5. S5 Fifth Fire: After heating and holding the S4 treated steel ingot at a temperature of T start ±10℃, the holding time is 2-5 hours per 100mm of drawing diameter. After exiting the furnace, continue to draw the blank to the large circle diameter of the blank using KD. Cut the blank at both ends according to the process requirements. Use KD to pinch out the water riser roll neck to obtain the semi-finished blank roll. S6 Sixth Fire: After heating and holding the semi-finished blank roll at a temperature of T start ±10℃, the holding time is 30-60 minutes for every 100mm of the diameter of the roll neck after the first fire. After exiting the furnace, KD stretches the roll necks at both ends to the roll neck size of the blank drawing, and then rounds them to produce the finished blank roll. Where Tinitial is the initial forging temperature, which ranges from 1100 to 1200℃.

2. The forging method according to claim 1, characterized in that, The steel ingot is a semi-steel casting ingot, and its composition by mass percentage is: C 1.0-1.6%, Si 0.2-0.7%, Mn 0.4-1.0%, Cr 1.0-2.0%, Ni 0.1-1.0%, Mo 0.2-0.8%, P and S ≤0.02%, with the remainder being iron and other impurity elements; and among the impurity elements, Cu+Pb+Sb+As+Bi+Sn+Zn<0.2%.

3. The forging method according to claim 1, characterized in that, The stepped heating curve mentioned in step S1 is as follows: Preheating stage: The steel ingot is heated to Tpre and held at that temperature, where Tpre is 750–850°C; Homogenization diffusion stage: Heat the steel ingot to Texpansion ±10℃ and hold it at that temperature. The heating rate is ≤50℃ / h, where Texpansion = Tinitial +30℃. Initial forging stage: The steel ingot is slowly cooled to Tinitial ±10℃ and held at that temperature, with a cooling rate ≤50℃ / h.

4. The forging method according to claim 3, characterized in that, The holding time for the preheating stage is h1, the holding time for the homogenization and diffusion stage is h2, and the holding time for the initial forging stage is h3. h1, h2, and h3 are determined according to the diameter of the steel ingot. h1 is held for 40 to 80 minutes per 100 mm, h2 is held for 2 to 5 hours per 100 mm, and h3 is held for 1 to 2 hours per 100 mm.

5. The forging method according to claim 1, characterized in that, The final forging temperature for each step is ≥850℃.

6. The forging method according to claim 1, characterized in that, The specific operation and parameters of step S2 are as follows: the pressing amount is ≥ 20% of the billet height, 90° flip, and pressing down one pass with the anvil offset.

7. The forging method according to claim 1, characterized in that, The specific operation and parameters of step S4 are as follows: the reduction amount is ≥ 20% of the billet height, 90° flip, and odd-even anvil arrangement.

8. The forging method according to claim 1, characterized in that, After obtaining the finished blanking roll in step S6, wait for the blanking roll to cool to 600±10℃ before putting the blanking roll into the forging furnace.

9. The forging method according to claim 1, characterized in that, The total forging ratio of the forging method is ≥3.

10. A forged semi-steel billet roll with high wear resistance and high accident resistance, characterized in that, The blanking roll is made by the forging method described in any one of claims 1 to 8. The hardness of the forged semi-steel blanking roll is 35 to 60 HSD, the room temperature yield strength is 480 to 800 MPa, and the tensile strength is 800 to 1300 MPa. The hardness difference within 200 mm of the surface is ≤3HS, which is suitable for opening deep hole grooves.

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