Forging method for working roll of large aluminum plate rolling mill

Abstract

The invention relates to a forging method for a working roll of a large aluminum plate rolling mill, belongs to the technical field of forging processes, and solves the problems of low steel ingot utilization rate, easiness in surface cracking, defects in the core of a steel ingot and the like in the forging process of similar products in the prior art. The invention provides a forging method for a working roll of a large aluminum plate rolling mill. The forging method comprises the steps of heat treatment, pre-drawing, upsetting, first-time drawing, second-time drawing and the like. According to the forging method, the problem of surface cracking in the electroslag ingot surface slag runner forging process can be effectively solved, meanwhile, by setting the reasonable pre-drawing ratio, upsetting ratio and drawing-out ratio and adding uniform diffusion before the heating number of upsetting and drawing-out compaction, the purpose of compacting the steel ingot core defect is achieved, organization preparation is provided for subsequent heat treatment, and the quality of the steel ingot core is improved. And the produced aluminum plate rolling mill working roll is excellent in performance, and is particularly suitable for forging production of large aluminum plate rolling mill working rolls with relatively strict quality requirements.

Description

Technical Field

[0001] The invention relates to the technical field of forging technology, and in particular to a forging method for a working roll of a large aluminum plate rolling mill. Background Art

[0002] The working rolls of large aluminum plate rolling mills are key components in aluminum plate hot rolling mills and are extremely difficult to manufacture. The working rolls of traditional Cr5 aluminum plate rolling mills are generally forged using the common forging method in the forging industry. The prepared working rolls generally have problems such as surface cracking and defects in the core of the steel ingot during the forging process; in addition, the quality of the product working layer is impure, the hardness uniformity is poor, the hardness is insufficient, and the wear resistance and anti-stripping properties are poor.

[0003] Therefore, it is necessary to develop a forging method specifically for the working rolls of large aluminum plate rolling mills. Summary of the invention

[0004] In view of the above analysis, an embodiment of the present invention aims to provide a forging method for working rolls of a large aluminum plate rolling mill, so as to solve the problems of low ingot utilization rate, easy surface cracking, defects in the core of the ingot, etc. in the prior art during the forging process; which leads to at least one of the problems of insufficient hardness of the working roll product, poor wear resistance and accident resistance.

[0005] The present invention provides a forging method for a working roll of a large aluminum plate rolling mill, and the forging method specifically comprises the following steps:

[0006] S1 first fire: the steel ingot is heat treated by a step-type heating curve. After the heat treatment, the upper and lower V-shaped anvils KD are used to pre-lengthen the steel ingot out of the furnace; the jaws are pressed at the bottom of the steel ingot, and the excess jaws are gas-cut according to the tonnage of the steel ingot, and the upper part of the steel ingot is gas-cut;

[0007] S2 Second Fire: After the steel ingot is heated and kept at the initial forging temperature T3 for a certain period of time, it is taken out of the furnace and upset to the required height of the process at an upset ratio of 1.5 to 2.5 using an upset tray and a spherical upset cover plate. The holding time is determined by 2 to 4 hours of holding for every 100 mm of the steel ingot diameter after the first fire KD;

[0008] S3 third fire: After the steel ingot is heated and kept at the initial forging temperature T3 for a certain period of time, it is taken out of the furnace and drawn to the required diameter by the process using upper and lower V-shaped anvils at a KD drawing ratio of 2.0 to 2.5. The holding time is determined by the second fire upsetting, which is 2 to 4 hours for every 100mm of the steel ingot diameter;

[0009] S4 Fourth Fire: After the steel ingot is heated and kept at the initial forging temperature T4 for a certain period of time, the holding time is determined by the holding time of 30 to 60 minutes for every 100mm of the steel ingot diameter after the third fire KD; after being taken out of the furnace, the upper flat anvil and the lower V anvil are used to draw it to the diameter of the blank, and the roller neck is pinched out at both ends of the billet water riser according to the length required by the process, and the finished product is drawn out;

[0010] Among them, T3 ranges from 1200 to 1250°C, and T4 is less than T3.

[0011] Specifically, the steel ingot is a high-carbon and high-molybdenum Cr5 material, and the specific composition of the material is C 0.3-0.8%, Si 0.4-0.8%, Mn 0.5-0.8%, P, S≤0.02%, Cr 4.5-5.5%, Ni≤0.60, Mo 0.4-0.8%, and V 0.05-0.25% by mass percentage.

[0012] Specifically, the specific parameters of the pre-drawing in step S1 are: the target size is determined according to the drawing ratio ≥ 1.5, and the pass reduction is 20% of the blank height;

[0013] The bottom cutting amount of the steel ingot is ≥200mm, the top cutting amount of the steel ingot is ≥150mm, and the steel ingot utilization rate is ≥70%

[0014] Specifically, the step-type heating curve in S1 is:

[0015] The first stage: the steel ingot is heated to temperature T1 and kept warm for a period of h1, where T1 is the temperature of the steel ingot when it is ingot, and h1 is kept warm for 30 to 60 minutes per 100 mm of the steel ingot diameter;

[0016] The second stage: the steel ingot is heated to temperature T2 and kept at this temperature for a period of h2, where T2 is the complete transformation temperature of austenite, ranging from 780 to 880°C, and h2 is kept at this temperature for 30 to 60 minutes per 100 mm of the steel ingot diameter, with a heating rate of ≤50°C / h;

[0017] The third stage: heat the steel ingot to temperature T3 and keep it warm for a period of time h3, where T3 is the initial forging temperature, ranging from 1200 to 1250°C, and h3 is 30 to 60 minutes per 100mm of the steel ingot diameter.

[0018] Specifically, the total forging ratio of the forging method is ≥4.5, the initial forging temperature is 1200-1250°C, and the final forging temperature of each fire is ≥850°C.

[0019] Specifically, the initial forging temperatures T4 and T3 satisfy: T4 = T3-30°C.

[0020] Furthermore, if the fourth firing of step S4 fails to produce the finished product, the fifth firing of step S5 is performed:

[0021] After the steel ingot is heated and kept at the initial forging temperature T5 for a certain period of time, the holding time is determined according to the diameter of the roller neck that has been taken out, and the upper flat anvil and the lower V anvil are used to continue the pulling operation until the finished product is obtained;

[0022] The initial forging temperatures T5 and T4 satisfy: T5 = T4-30°C.

[0023] Specifically, the specific operation of step S3 is: after being taken out of the furnace and stretched, after one pass of compaction, the half anvil is turned over by 90 degrees and pressed again, and the total number of compaction passes is 8 to 12.

[0024] Specifically, the specific operation of pinching out the roller neck and stretching out the finished product in step S4 is: stretching the small circles at both ends from the middle to the two ends to the size of each step, and gas cutting the excess length to produce the finished product.

[0025] The present invention also provides a large aluminum plate rolling mill working roll, the working roll is made by the forging method, the core of the product is dense, the cast defects are fully improved, the surface purity is high, and the SN322-11 flaw detection standard is met. The structure is uniform, the hardness uniformity reaches ±1HSD, the total amount of carbides in the structure increases, the type of carbides changes, the hardenability is improved, the hardness reaches ≥80HSD, and the wear resistance and spalling resistance of the product are improved.

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

[0027] 1. The present invention provides a forging method specifically used for working rolls of large aluminum plate rolling mills, and the forging method has a good effect on controlling surface cracks of steel ingots.

[0028] After the steel ingot is ingoted, it is heated by a step-type heating curve to prevent cracks on the surface and core of the steel ingot due to tissue stress and temperature stress; in particular, the special step-type heating curve recommended by the present invention has a better effect;

[0029] After the steel ingot is heated and discharged from the furnace for the first time, a pre-pulling process is set up to open the deep slag grooves on the surface of the electroslag ingot through pre-pulling, so as to avoid folding the slag grooves during the second fire upsetting and causing fractures. More preferably, pre-pulling breaks the cast structure on the surface of the steel ingot through a small deformation, reduces the generation of upsetting cracks, and also prepares the structure for subsequent high-temperature diffusion.

[0030] Furthermore, the final forging temperature of each fire is strictly controlled to be ≥850℃, and the forging is stopped before carbides precipitate on the surface to avoid forging cracks caused by network carbides.

[0031] 2. The forging method provided by the present invention can compact the defects in the core of the steel ingot, refine the grains, and improve the toughness and strength of the product. The pre-drawing fire with a drawing ratio ≥ 1.5 is set in S1, which increases the total forging ratio and makes the grains finer; multi-directional upsetting and drawing can make the forging structure more uniform and denser. At the same time, the larger upsetting ratio and KD drawing ratio provided by the present invention are helpful to compact the defects in the core of the steel ingot and improve the toughness and strength. This forging method increases the insulation time during heating before forging in the upsetting fire and the KD compaction fire, respectively, in order to achieve high-temperature diffusion, reduce element segregation, and uniform the structure through long-term insulation, thereby improving the toughness and strength of the product. This forging method reduces the initial forging temperature in the fourth and fifth fires, in order to avoid heating without a forging ratio, excessive growth of grains, and the occurrence of grass-shaped waves in flaw detection.

[0032] 3. The aluminum plate rolling mill working roll prepared by the forging method provided by the present invention has high purity, uniform structure, high hardness, good wear resistance and improved spalling resistance. The selected high-carbon and high-molybdenum Cr5 material has slightly higher C and Mo contents than the traditional Cr5 material, the total amount of carbides in the structure increases, the type of carbides changes, the hardness is higher, and the wear resistance is better; multi-directional upsetting can make the forging structure more uniform and the surface hardness of the product more uniform; the selected electroslag smelting steel ingot has pure product quality, good spalling resistance and better use effect.

[0033] In the present invention, the above-mentioned technical solutions can also be combined with each other to achieve more preferred combination solutions. Other features and advantages of the present invention will be described in the subsequent description, and some advantages can become obvious from the description, or can be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the contents particularly pointed out in the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings are only for the purpose of illustrating particular embodiments and are not to be considered limiting of the present invention. Like reference symbols denote like components throughout the drawings.

[0035] Figure 1 It is a schematic diagram of the step-type heating curve in the first fire;

[0036] Figure 2 This is a process diagram of the working roll blank in Example 1;

[0037] Figure 3 This is a step-type heating curve diagram in Example 1;

[0038] Figure 4 This is a schematic diagram of the pressure jaws and gas cutting waste in Example 1;

[0039] Figure 5 This is the forging blanking diagram in Example 1;

[0040] Figure 6 This is a step-type heating curve diagram in Example 2;

[0041] Figure 7 This is the step heating curve diagram in Example 3. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings, wherein the accompanying drawings constitute a 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 used to limit the scope of the present invention.

[0043] The working rolls of traditional Cr5 aluminum plate rolling mills have prominent quality problems such as impure working layer, poor accident resistance, unstable performance, etc. The high-carbon and high-molybdenum Cr5 material selected by the present invention has slightly higher C and Mo contents than the traditional Cr5 material, the total amount of carbides in the structure increases, the type of carbides changes, the hardenability is improved, and the wear resistance and spalling resistance of the product are improved.

[0044] However, this material also has its inherent defects. When the C and Mo content of the material is increased and the working rolls of large aluminum plate rolling mills made of this material are prepared by traditional forging process, the original defects in the center of the steel ingot solidify become larger. At the same time, the high C content can easily cause surface cracking during the forging process.

[0045] Based on the above technical difficulties, the forging method provided by the present invention adopts special curve heating, high-temperature diffusion homogenization, increasing the number of pre-drawing fires, multi-directional forging, and lowering the heating temperature of the finished product, which not only effectively alleviates the surface crack problem, but also fully improves the serious defects in the core, and the final product has excellent comprehensive performance.

[0046] The present invention provides a forging method for a working roll of a large aluminum plate rolling mill, and the forging method specifically comprises the following steps:

[0047] S1 first fire: the steel ingot is heat treated by a step-type heating curve. After the heat treatment, the upper and lower V-shaped anvils KD are used for pre-drawing after the steel ingot is taken out of the furnace, and the drawing ratio is ≥1.5; the bottom of the steel ingot is pressed with a jaw, and the excess jaw material is gas-cut according to the tonnage of the steel ingot, and the upper part of the steel ingot is gas-cut;

[0048] This step specifically requires that the pre-pulling length ratio be ≥1.5, which cannot be too small or too large. The purpose of setting up the pre-pulling is, on the one hand, to open the uneven and deep slag grooves on the surface of the electroslag ingot through pre-pulling, so as to avoid folding the slag grooves during the second fire upsetting and causing fractures. At the same time, the pre-pulling breaks the cast structure on the surface of the ingot through a certain amount of deformation, thereby reducing the occurrence of upsetting cracks. On the other hand, pre-pulling can shorten the distance between dendrites and improve the subsequent high-temperature diffusion effect. If the pre-pulling ratio is too small, the cast dendrites will change very limitedly with deformation, and the effect of pre-deformation on the high-temperature diffusion homogenization process will be very small, so the pre-deformation will lose its function and significance; if the pre-pulling ratio is too large, the dendrite arms and the materials between the dendrites will extend along the forging direction, resulting in banded segregation, which is difficult to eliminate by subsequent high-temperature diffusion.

[0049] S2 Second Fire: After the steel ingot is heated and kept at the initial forging temperature T3 for a certain period of time, it is taken out of the furnace and upset to the required height of the process at an upset ratio of 1.5 to 2.5 using an upset tray and a spherical upset cover plate. The holding time is determined by 2 to 4 hours of holding for every 100 mm of the steel ingot diameter after the first fire KD;

[0050] After the first step of pre-drawing, the cast structure of the ingot is improved to a certain extent, and the dendrite structure becomes denser. This step extends the holding time at the initial forging temperature. The purpose is to achieve high-temperature diffusion homogenization effect through long-term high-temperature holding, reduce the micro-segregation of elements between dendrites, and improve forging performance. The longer the high-temperature diffusion time, the better the diffusion effect. However, after diffusion to a certain extent, the element concentration gradient gradually decreases. At this time, increasing the diffusion time will slow down the homogenization effect, waste energy, and even lead to coarse grains. Therefore, the holding time cannot be insufficient or too long.

[0051] S3 third fire: After the steel ingot is heated and kept at the initial forging temperature T3 for a certain period of time, it is taken out of the furnace and drawn to the required diameter by the process using upper and lower V-shaped anvils at a KD drawing ratio of 2.0 to 2.5. The holding time is determined by the second fire upsetting, which is 2 to 4 hours for every 100mm of the steel ingot diameter;

[0052] S4 Fourth Fire: After the steel ingot is heated and kept at the initial forging temperature T4 for a certain period of time, the holding time is determined by the holding time of 30 to 60 minutes for every 100mm of the steel ingot diameter after the third fire KD; after being taken out of the furnace, the upper flat anvil and the lower V anvil are used to draw it to the diameter of the blank, and the roller neck is pinched out at both ends of the billet water riser according to the length required by the process, and the finished product is drawn out;

[0053] The special design of this step is that, since the remaining forging deformation is small, generally 1.0 to 1.5, in order to avoid the small deformation causing coarse grains in the core of the forging, affecting the core flaw detection quality and performance, the initial forging temperature is lowered and the holding time is shortened.

[0054] Among them, T3 ranges from 1200 to 1250°C, and T4 is less than T3.

[0055] Specifically, the steel ingot is a high-carbon and high-molybdenum Cr5 material, and the specific composition of the material is C 0.3-0.8%, Si 0.4-0.8%, Mn 0.5-0.8%, P, S≤0.02%, Cr 4.5-5.5%, Ni≤0.60, Mo 0.4-0.8%, and V 0.05-0.25% by mass percentage.

[0056] Furthermore, the C and Mo contents of the high-carbon and high-molybdenum Cr5 material are slightly increased compared to the traditional Cr5 material, the total amount of carbides in the structure increases, the type of carbides changes, the hardenability improves, and the wear resistance and spalling resistance of the product improve. Due to the increase in the C and Mo content of the material, the original defects in the core of the steel ingot solidify become larger, and the high C content is likely to cause surface cracking during the forging process. The forging method provided by the present invention effectively reduces the problem of surface cracks by adopting methods such as special curve heating, high-temperature diffusion homogenization, increasing the number of pre-drawing fires, multi-directional forging, and reducing the heating temperature of the finished product. At the same time, the serious defects in the core are fully improved, and the comprehensive performance of the final product is excellent.

[0057] Specifically, the specific parameters of the pre-drawing in step S1 are: the target size is determined according to the drawing ratio ≥ 1.5, and the pass reduction is 20% of the blank height;

[0058] The bottom resection of the steel ingot is ≥200 mm, the upper resection of the steel ingot is ≥150 mm, and the utilization rate of the steel ingot is ≥70%. The forging method adopts electroslag ingots. Compared with traditional top-cast ingots, the utilization rate of electroslag ingots is improved, reducing material waste.

[0059] Specifically, the step-type heating curve in S1 is:

[0060] The first stage: the steel ingot is heated to temperature T1 and kept warm for a period of h1, where T1 is the temperature of the steel ingot when it is ingot, and h1 is kept warm for 30 to 60 minutes per 100 mm of the steel ingot diameter;

[0061] The second stage: the steel ingot is heated to temperature T2 and kept at this temperature for a period of h2, where T2 is the complete transformation temperature of austenite, ranging from 780 to 880°C, h2 is kept at this temperature for 30 to 60 minutes per 100mm of the steel ingot size, and the heating rate is ≤50°C / h;

[0062] The third stage: heat the steel ingot to temperature T3 and keep it warm for a period of time h3, where T3 is the initial forging temperature, ranging from 1200 to 1250°C, and h3 is 30 to 60 minutes per 100mm of the steel ingot diameter. The heating rate can be based on the power of the forging heating furnace, and there is no restriction requirement.

[0063] Specifically, a step-type heating curve is set, with T1 section achieving uniform temperature, T2 section achieving complete austenite transformation, and T3 section heating to the initial forging temperature. The insulation time of each section is determined according to the diameter and heated through. The heating rate is controlled to avoid tensile stress in the inner and outer layer materials due to temperature stress and structural stress, thereby generating cracks.

[0064] Specifically, the total forging ratio of the forging method is ≥4.5, the initial forging temperature is 1200-1250°C, and the final forging temperature of each fire is ≥850°C. In actual implementation, due to certain errors in temperature control of industrial equipment, a maximum fluctuation space of ±10°C is allowed. It is worth noting that the final forging temperature is controlled above 850°C as much as possible. If the actual final forging is lower than 850°C due to temperature fluctuations, it may cause more obvious structural defects.

[0065] Specifically, the initial forging temperature T4 and T3 satisfy: T4 = T3-30° C. Since the remaining forging deformation is small, generally 1.0-1.5, in order to avoid the coarse grains in the core of the forging due to the small deformation, which affects the quality and performance of the core flaw detection, the initial forging temperature is reduced and the holding time is shortened.

[0066] Specifically, if the fourth firing of step S4 fails to produce the finished product, the fifth firing of step S5 is performed:

[0067] After the steel ingot is heated and kept at the initial forging temperature T5 for a certain period of time, the holding time is determined according to the diameter of the roller neck that has been taken out, and the upper flat anvil and the lower V anvil are used to continue the drawing operation until the finished product is obtained; the initial forging temperature T5 and T4 meet: T5 = T4-30 ° C. Here, since the remaining forging deformation is further reduced, the initial forging temperature is further reduced.

[0068] Specifically, the specific operation of step S3 is: after being taken out of the furnace and stretched, after one pass of compaction, the half anvil is turned over by 90 degrees and pressed again, and the total number of compaction passes is 8 to 12.

[0069] Specifically, the specific operation of pinching out the roller neck and stretching out the finished product in step S4 is: stretching the small circles at both ends from the middle to the two ends to the size of each step, and gas cutting the excess length to produce the finished product.

[0070] The present invention also provides a large aluminum plate rolling mill working roll, the working roll is made by the forging method, the core structure of the product is dense, the cast defects are fully improved, the surface purity is high, and the SN322-11 flaw detection standard is met. The structure is uniform, the hardness uniformity reaches ±1HSD, the total amount of carbides in the structure increases, the type of carbides changes, the hardenability is improved, the structure is tempered martensite + fine-grained carbide, the hardness reaches ≥80HSD, and the wear resistance and spalling resistance of the product are improved.

[0071] Examples and Comparative Examples

[0072] Example 1

[0073] According to the blank size ( Figure 2 ), select the appropriate steel ingot by weight. In this case, 70T electroslag steel ingot is used for forging production, with a utilization rate of 71.5%. The specific composition of the material is calculated by mass percentage: C0.67%, Si 0.47%, Mn 0.50%, P0.01%, S 0.005%, Cr 5.12%, Ni 0.40%, Mo 0.79%, V 0.10%.

[0074] First fire: After the ingot comes, press Figure 3 The curve performs pre-forging heating and heat preservation. The pre-drawn length of the KD out of the furnace is Φ1600mm×4340mm, and the pressing amount is 20% of the billet height. The bottom of the steel ingot is 400mm. The jaw size depends on the inner diameter of the matching upsetting plate, which is convenient for the subsequent fire operation machine to clamp. Gas cutting excess clamp handle, gas cutting steel ingot upper discarded material ≥250mm, such as Figure 4 shown.

[0075] Second firing: Initial forging furnace temperature is 1250±10℃, keep warm for 35h, select a suitable upsetting drain plate after taking out of the furnace, place the billet between the upsetting drain plate and the upsetting cover plate, place the jaws on the inner hole of the upsetting drain plate, and upset to H=1900mm.

[0076] The third firing: the initial forging furnace temperature is 1250±10℃, and the temperature is kept for 35h. After the KD is taken out of the furnace, it is stretched to Φ1400mm. The full anvil is fed. After pressing one pass, it is turned 90° and half the anvil is offset, and the next pass is pressed. The total number of passes is 10.

[0077] Fourth fire: Initial forging furnace temperature 1220±10℃, keep warm for 10h, take out of furnace, draw the upper flat and lower V anvil to Φ1200mm, press Figure 5 Cut the material and draw the small circles at both ends to the blank Figure 1 Each step is sized and the excess length is gas cut to produce the finished product.

[0078] There is no cracking on the surface during the forging process, the production process is smooth, and the finished product is produced after four heat treatments. The hardness after the final heat treatment is 80~82HSD (81±1HSD). The defect equivalent of the working layer is ≤Ф1, and the defect equivalent of other areas is ≤Ф3, which meets the requirements of the flaw detection standard.

[0079] Example 2

[0080] According to the size and weight of the blank, the appropriate steel ingot is selected. In this case, 75T electroslag steel ingot is used for forging production, with a utilization rate of 71%. Specific information of the material: C 0.69%, Si 0.50%, Mn 0.60%, P 0.015%, S 0.005%, Cr5.34%, Ni 0.35%, Mo 0.80%, V 0.15%.

[0081] First fire: After the ingot is received, it is heated according to the special step heating curve Figure 6 Perform pre-forging heating and heat preservation. The pre-drawn length of the KD out of the furnace is Φ1650mm×4500mm, and the pressing amount is 20% of the billet height. The bottom of the ingot is 400mm. The jaw size depends on the inner diameter of the matching upsetting plate, which is convenient for the subsequent fire operation machine to clamp. Gas cutting excess clamp handle, gas cutting steel ingot upper discarded material ≥250mm.

[0082] Second firing: Initial forging furnace temperature is 1240±10℃, keep warm for 40h, select a suitable upsetting drain plate after taking out of the furnace, place the billet between the upsetting drain plate and the upsetting cover plate, place the jaws on the inner hole of the upsetting drain plate, and upset to H=1900mm.

[0083] The third firing: the initial forging furnace temperature is 1240±10℃, and the temperature is kept for 40h. After the KD is taken out of the furnace, it is stretched to Φ1450mm. The full anvil is fed. After pressing one pass, it is turned 90° and half the anvil is offset, and the next pass is pressed. The total number of passes is 10.

[0084] Fourth firing: Initial forging furnace temperature is 1210±10℃, keep warm for 10h, take out of furnace and stretch the upper flat and lower V anvil to Φ1250mm, cut the material according to the required weight of the roll neck, stretch the small circles at both ends to the blank size in turn, cut the excess length by gas, and produce the finished product.

[0085] There is no cracking on the surface during the forging process, the production process is smooth, and the finished product is produced after four heat treatments. The hardness after the final heat treatment is 81~83HSD (82±1). The defect equivalent of the working layer is ≤Ф2, and the defect equivalent of other areas is ≤Ф3, which meets the requirements of the flaw detection standard.

[0086] Example 3

[0087] According to the size and weight of the blank, the appropriate steel ingot is selected. In this case, 80T electroslag steel ingot is used for forging production, with a utilization rate of 70.5%. Specific information of the material: C 0.70%, Si 0.55%, Mn 0.65%, P 0.015%, S 0.005%, Cr5.30%, Ni 0.40%, Mo 0.80%, V 0.15%.

[0088] First fire: After the ingot is received, it is heated according to the special step heating curve Figure 7Perform pre-forging heating and heat preservation. The pre-drawn length of the KD out of the furnace is Φ1700mm×4550mm, and the pressing amount is 20% of the billet height. The bottom of the ingot is 450mm. The jaw size depends on the inner diameter of the matching upsetting plate, which is convenient for the subsequent fire operation machine to clamp. Gas cutting excess clamp handle, gas cutting steel ingot upper discard ≥250mm.

[0089] Second firing: Initial forging furnace temperature is 1230±10℃, keep warm for 50h, select a suitable upsetting drain plate after taking out of the furnace, place the billet between the upsetting drain plate and the upsetting cover plate, place the jaws on the inner hole of the upsetting drain plate, and upset to H=1950mm.

[0090] The third firing: the initial forging furnace temperature is 1230±10℃, and the temperature is kept for 50h. After the KD is taken out of the furnace, it is stretched to Φ1500mm. The full anvil is fed. After pressing one pass, it is turned 90° and half the anvil is offset, and the next pass is pressed. The total number of passes is 10.

[0091] The fourth firing: the initial forging furnace temperature is 1200±10℃, and the temperature is kept for 15h. After being taken out of the furnace, the upper flat and lower V anvil are drawn to Φ1300mm. The material is cut according to the required weight of the roll neck, and the roll neck is drawn to a diameter of Φ1000mm, and then returned to the furnace for heating.

[0092] The fifth firing: the initial forging furnace temperature is 1170±10℃, kept warm for 7h, and then the upper flat and lower V-anvil are used to lengthen the roll neck to the blank size to produce the finished product.

[0093] There is no cracking on the surface during the forging process, the production process is smooth, and the finished product is produced after five heat treatments. The hardness after the final heat treatment is 82~84HSD (83±1). The defect equivalent of the working layer is ≤Ф2, and the defect equivalent of other areas is ≤Ф4, which meets the requirements of the flaw detection standard.

[0094] Comparative Example 1

[0095] According to the size and weight of the blank, the appropriate steel ingot is selected. In this case, 83T vacuum smelting and pouring steel ingot is used for forging production, with a utilization rate of 60.1%. Specific information of the material: C 0.65%, Si 0.55%, Mn 0.65%, P 0.015%, S0.005%, Cr 5.10%, Ni 0.40%, Mo 0.75%, V 0.15%.

[0096] First fire: put the ingot directly into the heating furnace, heat to 1250℃, keep warm for 10 hours and then take it out of the furnace. Press the jaws, gas cut the bottom of the ingot nozzle, gas cut the excess jaws and discard the material.

[0097] Second firing: Initial forging furnace temperature is 1250±10℃, keep warm for 22h, select a suitable upsetting drain plate after taking out of the furnace, place the billet between the upsetting drain plate and the upsetting cover plate, place the jaws on the inner hole of the upsetting drain plate, and upset to H=1850mm.

[0098] The third firing: the initial forging furnace temperature is 1250±10℃, and the temperature is kept for 22h. After the KD is taken out of the furnace, it is stretched to Φ1400mm. The full anvil is fed. After pressing one pass, it is turned 90° and half the anvil is offset, and the next pass is pressed. The total number of passes is 10.

[0099] Fourth firing: Initial forging furnace temperature is 1220±10℃, keep warm for 10h, take out of furnace and stretch to Φ1200mm with upper flat and lower V anvil, cut the material according to the required weight of roll neck, stretch the small circles at both ends to the size of blank in turn, cut the excess length by gas, and produce the finished product.

[0100] The fifth firing: the initial forging furnace temperature is 1190±10℃, kept warm for 7h, and then the upper flat and lower V-anvil are used to lengthen the roll neck to the blank size to produce the finished product.

[0101] The double vacuum steel ingots used in the steel ingots have no pre-drawing process, and the holding time before upsetting and KD drawing does not take into account the homogenization time. The surface of the double vacuum ingot is easy to crack, and longitudinal cracks are generated on the surface of the upsetting fire, which increases the cleaning process. The homogenization time is not considered, and the hardness after the final heat treatment is 80-85HSD, and the uniformity is ±2.5HSD. The defect equivalent of the working layer is ≤Ф2, and the defect equivalent of other areas is ≤Ф8. The quality of the core does not meet the requirements of the flaw detection standard.

[0102] Comparative Example 2

[0103] According to the size and weight of the blank, the appropriate steel ingot is selected. In this case, 80T vacuum smelting and pouring steel ingot is used for forging production, with a utilization rate of 62%. Specific information of the material: C 0.65%, Si 0.55%, Mn 0.65%, P 0.015%, S0.005%, Cr 5.10%, Ni 0.40%, Mo 0.75%, V 0.15%.

[0104] First fire: After the ingot arrives, it is directly placed in the heating furnace, heated to 1250℃, and kept warm for 50 hours before being taken out of the furnace. Press the jaws, pre-draw the length to Φ1700mm×4550mm, gas-cut the bottom of the ingot nozzle, and gas-cut the excess jaws to discard.

[0105] Second firing: Initial forging furnace temperature is 1250±10℃, keep warm for 20h, select a suitable upsetting drain plate after taking out of the furnace, place the billet between the upsetting drain plate and the upsetting cover plate, place the jaws on the inner hole of the upsetting drain plate, and upset to H=1850mm.

[0106] The third firing: the initial forging furnace temperature is 1250±10℃, and it is kept warm for 20h. After the KD is taken out of the furnace, it is stretched to Φ1400mm. The full anvil is fed, and after pressing one pass, it is turned 90° and half the anvil is offset, and the next pass is pressed. The total number of passes is 10.

[0107] Fourth firing: Initial forging furnace temperature is 1220±10℃, keep warm for 10h, take out of furnace and stretch to Φ1200mm with upper flat and lower V anvil, cut the material according to the required weight of roll neck, stretch the small circles at both ends to the size of blank in turn, cut the excess length by gas, and produce the finished product.

[0108] The fifth firing: the initial forging furnace temperature is 1190±10℃, kept warm for 7h, and then the upper flat and lower V-anvil are used to lengthen the roll neck to the blank size to produce the finished product.

[0109] The double vacuum steel ingot selected for the steel ingot takes the homogenization time into consideration during the first heating, and the homogenization time is not considered during the holding time before pre-drawing, upsetting and KD drawing, resulting in poor diffusion effect in the core. The hardness after the final heat treatment is 80-84HSD, and the uniformity is ±2HSD. The defect equivalent of the working layer is ≤Ф2, and the defect equivalent of other areas is ≤Ф6. The quality of the core does not meet the requirements of the flaw detection standard.

[0110] In summary, the core structure of the large aluminum plate rolling mill work roll product provided by the present invention is dense, the as-cast defects are fully improved, the surface purity is high, and it meets the SN322-11 flaw detection standard. The structure is uniform, the hardness uniformity reaches ±1HSD, the total amount of carbides in the structure increases, the type of carbides changes, the hardenability is improved, the hardness reaches ≥80HSD, and the wear resistance and spalling resistance of the product are improved.

[0111] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by any technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A forging method for a large aluminum plate rolling mill working roll, characterized in that: The forging method specifically comprises the following steps: S1 first fire: the steel ingot is heat treated by a step-type heating curve. After the heat treatment, the upper and lower V-shaped anvils KD are used to pre-lengthen the steel ingot out of the furnace; the jaws are pressed at the bottom of the steel ingot, and the excess jaws are gas-cut according to the tonnage of the steel ingot, and the upper part of the steel ingot is gas-cut; S2 Second Fire: After the steel ingot is heated and kept at temperature T3 for a certain period of time, it is taken out of the furnace and upset to the required height of the process at an upset ratio of 1.5 to 2.5 using an upset tray and a spherical upset cover plate. The holding time is determined by 2 to 4 hours of holding for every 100 mm of the steel ingot diameter after the first fire KD; S3 third fire: After the steel ingot is heated and kept at temperature T3 for a certain period of time, it is taken out of the furnace and drawn to the required diameter by the process using upper and lower V-shaped anvils at a KD drawing ratio of 2.0 to 2.

5. The holding time is determined by the second fire upsetting, which is 2 to 4 hours for every 100mm of the steel ingot diameter; S4 Fourth Fire: After the steel ingot is heated and kept at temperature T4 for a certain period of time, the holding time is determined by the holding time of 30 to 60 minutes for every 100mm of the steel ingot diameter after the third fire KD; after being taken out of the furnace, the upper flat anvil and the lower V anvil are used to pull it to the diameter of the blank, and the roller neck is pinched out at both ends of the billet water riser according to the length required by the process, and the finished product is pulled out; Among them, T3 ranges from 1200 to 1250°C, and T4 is less than T3.

2. The forging method according to claim 1, characterized in that: The steel ingot is a high-carbon and high-molybdenum Cr5 material, and the specific composition of the material is C 0.3-0.8%, Si 0.4-0.8%, Mn 0.5-0.8%, P, S≤0.02%, Cr 4.5-5.5%, Ni≤0.60, Mo 0.4-0.8%, V 0.05-0.25% by mass percentage.

3. The forging method according to claim 1, characterized in that: The specific parameters of the pre-drawing in step S1 are: the target size is determined according to the drawing ratio ≥ 1.5, and the pass reduction is 20% of the blank height; The amount of the bottom of the steel ingot cut off is ≥200 mm, the amount of the top of the steel ingot cut off is ≥150 mm, and the utilization rate of the steel ingot is ≥70%.

4. The forging method according to claim 1, characterized in that: In S1, the step-type heating curve is specifically: The first stage: the steel ingot is heated to temperature T1 and kept warm for a period of h1, where T1 is the temperature of the steel ingot when it is ingot, and h1 is kept warm for 30 to 60 minutes per 100 mm of the steel ingot diameter; The second stage: the steel ingot is heated to temperature T2 and kept at this temperature for a period of h2, where T2 is the complete transformation temperature of austenite, ranging from 780 to 880°C, and h2 is kept at this temperature for 30 to 60 minutes per 100 mm of the steel ingot diameter, with a heating rate of ≤50°C / h; The third stage: heat the steel ingot to temperature T3 and keep it warm for a period of time h3, where T3 is the initial forging temperature, ranging from 1200 to 1250°C, and h3 is kept warm for 30 to 60 minutes per 100mm of the steel ingot diameter.

5. The forging method according to claim 1, characterized in that: The total forging ratio of the forging method is ≥4.5, the initial forging temperature is 1200-1250°C, and the final forging temperature of each fire is ≥850°C.

6. The forging method according to claim 1, characterized in that: The initial forging temperatures T4 and T3 satisfy: T4 = T3-30°C.

7. The forging method according to claim 1, characterized in that: If the fourth fire of step S4 fails to produce the finished product, the fifth fire of step S5 is performed: After the steel ingot is heated and kept at the initial forging temperature T5 for a certain period of time, the holding time is determined according to the diameter of the roller neck that has been taken out, and the upper flat anvil and the lower V anvil are used to continue the pulling operation until the finished product is obtained; The initial forging temperatures T5 and T4 satisfy: T5 = T4-30°C.

8. The forging method according to claim 1, characterized in that: The specific operation of step S3 is: after being taken out of the furnace and stretched, after one pass of compaction, the anvil is turned over by 90 degrees and half-staggered, and the next pass is compacted, and the total number of passes is 8 to 12.

9. The forging method according to claim 1, characterized in that: The specific operation of pinching out the roller neck and stretching out the finished product in step S4 is: stretching the small circles at both ends from the middle to the two ends to the size of each step, and gas cutting the excess length to produce the finished product.

10. A working roll of a large aluminum plate rolling mill, characterized in that: The working roll is made by the forging method described in any one of claims 1 to 9, meets the SN322-11 flaw detection standard, has a hardness of ≥80HSD, and a hardness uniformity of ±1HSD.

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