A method of forging a work roll for a large aluminum sheet rolling mill

Abstract

The present application relates to a kind of large aluminum plate rolling mill work roll forging method, belong to the technical field of forging process, solve the low utilization rate of steel ingot in the forging process of similar products in the prior art, prone to surface cracking, steel ingot core exists defect and other problems.The present application provides a kind of large aluminum plate rolling mill work roll forging method, including heat treatment, pre-drawing, upsetting, first drawing, second drawing and other steps.The forging method can effectively solve the problem of surface cracking in the surface slag ditch of electroslag ingot in the forging process, while setting reasonable pre-drawing ratio, upsetting ratio and drawing ratio, and increasing homogenization diffusion before upsetting and drawing compaction fire, to achieve the purpose of compaction steel ingot core defect, provide organization preparation for subsequent heat treatment, the performance of aluminum plate rolling mill work roll produced is excellent, especially suitable for the forging production of large aluminum plate rolling mill work roll with relatively strict quality requirements.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of forging process technology, in particular to a kind of large aluminum plate rolling mill work roll forging method. BACKGROUND

[0002] Large aluminum plate rolling mill work roll is the key component in aluminum plate hot rolling mill group, and the manufacturing difficulty is extremely great.The traditional Cr5 aluminum plate rolling mill work roll generally adopts the general forging method in forging industry, and the work roll prepared generally has problems such as surface cracking in the forging process, defects in the core of the ingot, etc.In addition, the product work layer quality is not pure, the hardness uniformity is poor, the hardness is insufficient, and the wear resistance and anti-peeling performance are poor.

[0003] Therefore, it is necessary to develop a kind of forging method special for large aluminum plate rolling mill work roll. SUMMARY

[0004] In view of the above analysis, the embodiments of the present application aim to provide a kind of large aluminum plate rolling mill work roll forging method, to solve the problems such as low utilization rate of ingot in the forging process, easy to crack on the surface, defects in the core of the ingot, etc., in the prior art;Further cause at least one of the problems such as insufficient hardness of work roll product, poor wear resistance and anti-accident performance.

[0005] The present application provides a kind of large aluminum plate rolling mill work roll forging method, the forging method specifically includes the following steps:

[0006] S1 first fire: the ingot is heat treated by using a step heating curve, after heat treatment, the KD pre-drawing is used to draw out after furnace;The bottom of the ingot is pressed with a jaw, and the excess jaw scrap is cut by gas cutting according to the tonnage of the ingot, and the upper scrap of the ingot is cut by gas cutting;

[0007] S2 second fire: after the ingot is heated at the initial forging temperature T3 for a certain time, the upsetting disc and the spherical upsetting cover plate are used to upset to the process required height according to the upsetting ratio of 1.5-2.5, and the holding time is determined according to 2-4h per 100mm of the diameter of the ingot after the KD of the first fire;

[0008] S3 third fire: after the ingot is heated at the initial forging temperature T3 for a certain time, the KD is used to draw out to the process required diameter according to the KD drawing ratio of 2.0-2.5, and the holding time is determined according to 2-4h per 100mm of the diameter of the ingot after the upsetting of the second fire;

[0009] S4 fourth fire: after the ingot is heated at the initial forging temperature T4 for a certain time, the holding time is determined according to 30-60min per 100mm of the diameter of the ingot after the KD of the third fire;The KD is used to draw out to the blank drawing diameter using the upper flat anvil and the lower V anvil, and the roll neck is pinched out according to the process required length at both ends of the billet water head, and the finished product is drawn out;

[0010] wherein T3 ranges from 1200 to 1250℃, and T4 < T3.

[0011] Specifically, the steel ingot is a high-carbon high-molybdenum Cr5 material, and the specific composition of the material is as follows in terms of mass percentage: 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%.

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

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

[0014] Specifically, the stepwise heating curve in S1 is as follows:

[0015] First stage: heating the steel ingot to a temperature T1 and keeping it for a time h1, wherein T1 is the temperature of the steel ingot when it is cast, and h1 is 30-60min per 100mm of the diameter of the steel ingot;

[0016] Second stage: heating the steel ingot to a temperature T2 and keeping it for a time h2, wherein T2 is the complete austenite transformation temperature, ranging from 780 to 880℃, and h2 is 30-60min per 100mm of the diameter of the steel ingot, and the heating rate is ≤50℃ / h;

[0017] Third stage: heating the steel ingot to a temperature T3 and keeping it for a time h3, wherein T3 is the initial forging temperature, ranging from 1200 to 1250℃, and h3 is 30-60min per 100mm of the diameter of the steel ingot.

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

[0019] Specifically, the initial forging temperature T4 and T3 satisfy: T4 = T3-30℃.

[0020] Further, if the fourth heating of step S4 fails to complete the finished product, the fifth heating of step S5 is performed:

[0021] After the steel ingot is heated at the initial forging temperature T5 for a certain time, the holding time is determined according to 30-60min per 100mm of the diameter of the rolled neck, and the drawing operation is continued using the upper anvil and the lower V anvil until the finished product is obtained;

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

[0023] Specifically, the specific operation of the step S3 is: after the tapping and elongation, the 90° half anvil is turned over after the completion of a pass, and the next pass is pressed, and the total pass is 8-12 passes.

[0024] Specifically, the specific operation of the step S4 is: the roll neck is pinched out, and the finished product is elongated, and the excess length is gas cut from the middle to the two ends to the size of each step.

[0025] The application also provides a large aluminum plate rolling mill working roll, which is made by the forging method, has a compact core structure, fully improved as-cast defects, high surface purity, meets the SN322-11 flaw detection standard, uniform structure, hardness uniformity of ±1HSD, increased total amount of carbide in the structure, changed carbide type, improved hardenability, hardness of ≥80HSD, and improved wear resistance and peeling resistance of the product.

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

[0027] 1. The application provides a forging method special for a large aluminum plate rolling mill working roll, which has a good effect on the control of surface cracks of the steel ingot.

[0028] The steel ingot is heated by a stepwise heating curve after coming out of the ingot, so as to prevent cracks on the surface and the core of the steel ingot due to organizational stress and temperature stress; in particular, the special stepwise heating curve recommended by the application has better effect.

[0029] After the first heating of the steel ingot, a pre-elongation process is set, which is to open the uneven and deep slag groove on the surface of the electroslag ingot through pre-elongation, so as to avoid folding of the slag groove during the second upsetting, thereby causing folding damage. More preferably, the pre-elongation breaks the as-cast structure on the surface of the steel ingot through small deformation, reduces the generation of upsetting cracks, and also prepares the structure for subsequent high-temperature diffusion.

[0030] Further, the final forging temperature of each fire is strictly controlled to be greater than or equal to 850 DEG C, the forging is stopped before the surface precipitates carbide, and the network carbide is avoided to cause the forging to crack.

[0031] 2、The forging method provided by the application can well compact the core defects of the steel ingot, refine the grains, and improve the toughness and strength of the product. The pre-drawing fire in S1 is set to have a drawing ratio of greater than or equal to 1.5, the total forging ratio is increased, and the grains are finer. Multi-direction upsetting and drawing can make the forging structure more uniform and more dense. Meanwhile, according to the large upsetting ratio and KD drawing ratio provided by the application, the core defects of the steel ingot can be compacted, and the toughness and strength can be improved. The heating before forging in the upsetting fire and the KD compacting fire in the forging method is increased in the holding time, and the purpose is to realize high-temperature diffusion, reduce element segregation, and uniform structure, so as to improve the toughness and strength of the product. The initial forging temperature in the fourth fire and the fifth fire is reduced, and the purpose is to avoid no-forging ratio heating, excessive grain growth, and the occurrence of grass-like wave problems in the flaw detection.

[0032] 3、The aluminum plate mill work roll prepared by the forging method provided by the application has high purity, uniform structure, high hardness, good wear resistance, and improved anti-peeling property. The selected high-carbon high-molybdenum Cr5 material has slightly higher C and Mo content than the traditional Cr5 material, the total amount of carbides in the structure is increased, the type of carbides is changed, the hardness is higher, and the wear resistance is better. Multi-direction upsetting and drawing can make the forging structure more uniform, and the uniformity of the surface hardness of the product is better. The selected electroslag refining steel ingot has pure product quality, good anti-peeling property, and better use effect.

[0033] In the application, the above technical solutions can be combined with each other to realize more preferred combination solutions. Other features and advantages of the application will be described in the subsequent specification, and some advantages will become apparent from the specification or be understood by implementing the application. The purposes and other advantages of the application can be realized and obtained from the contents specifically indicated in the specification and the drawings. BRIEF DESCRIPTION OF DRAWINGS

[0034] The accompanying drawings are included to provide a further understanding of the application and are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description serve to explain the principles of the application. In the drawings:

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

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

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

[0038] Figure 4 It is a schematic diagram of the pressure tong opening and gas cutting scrap in Example 1;

[0039] Figure 5 It is a blanking diagram of the forged piece in Example 1;

[0040] Figure 6 A stepwise heating curve diagram in Example 2;

[0041] Figure 7 A stepwise heating curve diagram in Example 3. DETAILED DESCRIPTION

[0042] The preferred embodiments of the present application will be described in detail below with reference to the drawings, which form a part of this application, and together with the description, illustrate the principles of the application, but are not intended to limit the scope of the application.

[0043] The traditional Cr5 aluminum plate rolling mill work roll has the prominent quality problems of impure working layer, poor accident resistance and unstable use performance. The high-carbon high-molybdenum Cr5 material selected in the application has slightly increased C and Mo contents compared with the traditional Cr5 material, the total amount of carbides in the structure is increased, the type of carbides is changed, the hardenability is improved, and the wear resistance and spalling resistance of the product are improved.

[0044] However, this kind of material also has its inherent defects. Due to the increase of C and Mo contents of the material, when the large aluminum plate rolling mill work roll of this kind of material is prepared by using the traditional forging process, the original defects of the ingot at the final core of solidification are large, and the high C content is easy to cause surface cracking during forging.

[0045] Based on the above technical problems, the forging method provided by the application effectively reduces the surface cracking problem, and the serious defects in the core are fully improved, and the comprehensive performance of the final product is superior.

[0046] The application provides a forging method of a large aluminum plate rolling mill work roll, and the forging method specifically comprises the following steps:

[0047] S1 first fire: the ingot is heat treated by using a stepwise heating curve, after heat treatment, the ingot is discharged by using an upper and lower V-shaped anvil KD for pre-drawing, and the drawing ratio is greater than or equal to 1.5; the bottom of the ingot is pressed by a jaw, the excess jaw scrap is cut by using a gas cutting device, and the upper scrap of the ingot is cut by using the gas cutting device;

[0048] The special requirement of this step is that the pre-drawing ratio is greater than or equal to 1.5, which cannot be too small or too large. The purpose of setting the pre-drawing is to open the uneven and deep slag groove on the surface of the electroslag ingot through pre-drawing, so as to avoid the folding of the slag groove during the second upsetting, thereby causing the folding damage. At the same time, the pre-drawing can break the cast structure on the surface of the ingot through a certain deformation, thereby reducing the generation of the upsetting crack. On the other hand, the pre-drawing can shorten the interdendritic distance and improve the subsequent high-temperature diffusion effect. If the pre-drawing ratio is too small, the cast dendrite changes very limitedly with the deformation, the pre-deformation has very small influence on the high-temperature diffusion homogenization process, and the pre-deformation loses the effect and significance. If the pre-drawing ratio is too large, the material of the dendrite arm and the interdendritic material extends along the forging direction, causing the banded segregation, and the subsequent high-temperature diffusion is difficult to eliminate the segregation.

[0049] S2 second fire: after the ingot is heated at the initial forging temperature T3 for a certain time, the ingot is taken out of the furnace, the upsetting disc and the spherical upsetting cover plate are used to upset the ingot to the process required height at the upsetting ratio of 1.5-2.5, and the holding time is determined according to 2-4 h per 100 mm of the diameter of the ingot 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 dendritic structure becomes more compact. The purpose of extending the holding time at the initial forging temperature in this step is to achieve the high-temperature diffusion homogenization effect through long-time high-temperature holding, thereby reducing the interdendritic element micro-segregation and improving the forging performance. The longer the high-temperature diffusion time is, the better the diffusion effect is. However, after the diffusion reaches a certain degree, the element concentration gradient gradually decreases. At this time, increasing the diffusion time has a slow homogenization effect, which wastes energy, and even causes the grain to become coarse. Therefore, the holding time cannot be insufficient or too long.

[0051] S3 third fire: after the ingot is heated at the initial forging temperature T3 for a certain time, the ingot is taken out of the furnace, the upper and lower V-shaped anvil is used to draw the ingot to the process required diameter at the KD drawing ratio of 2.0-2.5, and the holding time is determined according to 2-4 h per 100 mm of the diameter of the ingot after the second fire KD;

[0052] S4 fourth fire: after the ingot is heated at the initial forging temperature T4 for a certain time, the holding time is determined according to 30-60 min per 100 mm of the diameter of the ingot after the third fire KD; the ingot is taken out of the furnace, the upper flat anvil and the lower V-shaped anvil are used to draw the ingot to the diameter of the blank drawing, the roll necks are cut out at both ends of the blank water head according to the process required length, and the finished product is drawn out;

[0053] The special design of this step is that the remaining forging deformation is small, generally 1.0-1.5. In order to avoid the small deformation leading to the coarse grain in the center of the forging, affecting the center flaw detection quality and performance, the initial forging temperature is reduced and the holding time is shortened.

[0054] T3 is in the range of 1200-1250℃, and T4 is less than T3.

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

[0056] Further, the high-carbon high-molybdenum Cr5 material has slightly increased C and Mo contents compared with the traditional Cr5 material, the total amount of carbides in the structure is increased, the type of carbides is changed, the hardenability is increased, and the wear resistance and spalling resistance of the product are increased. Due to the increased C and Mo contents of the material, the original defects in the center of the steel ingot during solidification are increased, and the high C content is prone to cause surface cracking during forging. The forging method provided by the application effectively reduces the surface cracking problem and fully improves the serious defects in the center, and the comprehensive performance of the final product is superior.

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

[0058] The cutting amount of the bottom of the steel ingot is ≥200mm, the cutting amount of the upper part of the steel ingot is ≥150mm, and the utilization rate of the steel ingot is ≥70%. The forging method uses an electroslag ingot, and compared with the traditional top-charging ingot, the utilization rate of the electroslag ingot is increased, and material waste is reduced.

[0059] Specifically, the step S1 is a step of heating the steel ingot according to a step-by-step heating curve.

[0060] The first stage is to heat the steel ingot to a temperature T1 and keep it for a period of time h1, wherein T1 is in the range of the temperature of the steel ingot when it is cast, and h1 is kept for 30-60min per 100mm of the diameter of the steel ingot;

[0061] The second stage is to heat the steel ingot to a temperature T2 and keep it for a period of time h2, wherein T2 is the complete transformation temperature of austenite, in the range of 780-880℃, and h2 is kept for 30-60min per 100mm of the size of the steel ingot, and the heating rate is ≤50℃ / h;

[0062] The third stage is to heat the steel ingot to a temperature T3 and keep it for a period of time h3, wherein T3 is the initial forging temperature, in the range of 1200-1250℃, and h3 is kept for 30-60min per 100mm of the diameter of the steel ingot. The heating rate is determined according to the power of the forging heating furnace, and no limitation is required.

[0063] Specifically, a stepped heating curve is set, T1 section realizes temperature uniformity, T2 section realizes complete austenite transformation, and T3 section is heated to the initial forging temperature. The holding time of each section can be determined according to the diameter to achieve heating penetration. The heating rate is controlled to avoid tensile stress of the inner and outer layers of the material due to temperature stress and organizational stress, thereby avoiding cracks.

[0064] Specifically, the total forging ratio of the forging method is greater than or equal to 4.5, the initial forging temperature is 1200-1250 DEG C, and the final forging temperature of each heating is greater than or equal to 850 DEG C. In actual implementation, due to the existence of certain errors in the temperature control of industrial equipment, a fluctuation space of plus or minus 10 DEG C is allowed. It is worth noting that the final forging temperature is controlled above 850 DEG C as much as possible. If the actual final forging is lower than 850 DEG C due to temperature fluctuation, it may cause obvious structural defects.

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

[0066] Specifically, if the fourth heating of the step S4 fails to complete the finished product, the fifth heating of the step S5 is performed.

[0067] After the ingot is heated at the initial forging temperature T5 for a certain time, the holding time is determined according to the diameter of the rolled neck, that is, 30-60 min per 100 mm of the diameter of the rolled neck, and the upper anvil and the lower V anvil are used to continue the lengthening operation until the finished product is obtained. The initial forging temperature T5 and T4 satisfy: T5=T4-30 DEG C. Here, since the remaining forging deformation is further reduced, the initial forging temperature is further reduced.

[0068] Specifically, the specific operation of the step S3 is as follows: after the ingot is rolled out, the anvil is turned over by 90 DEG after one pass is completed, and the next pass is pressed, and the total pass is 8-12 passes.

[0069] Specifically, the specific operation of the step S4 for cutting out the rolled neck and lengthening the finished product is as follows: the small circles at both ends are lengthened to the size of each step in sequence from the middle to both ends, the excess length is cut by gas cutting, and the finished product is obtained.

[0070] The application also provides a large aluminum plate rolling mill work roll, which is prepared by the forging method, has dense center structure, fully improved as-cast defects, high surface purity, satisfies the SN322-11 flaw detection standard, uniform structure, hardness uniformity of ±1HSD, increased total amount of carbides in the structure, changed carbide type, improved hardenability, structure of tempered martensite + fine-grained carbide, hardness of ≥80HSD, and improved wear resistance and anti-peeling property of the product.

[0071] Examples and Comparative Examples

[0072] Example 1

[0073] According to the blank size ( Figure 2 ), select an appropriate steel ingot by weight. This case uses a 70T electroslag ingot forging, achieving a utilization rate of 71.5%. The specific material composition, by mass percentage, is: C 0.67%, Si 0.47%, Mn 0.50%, P 0.01%, S 0.005%, Cr 5.12%, Ni 0.40%, Mo 0.79%, and V 0.10%.

[0074] First fire: After the ingot comes, press Figure 3 The curve is heated and kept warm before forging. The KD pre-drawn out of the furnace is Φ1600mm×4340mm, and the reduction is 20% of the billet height. The bottom of the ingot is 400mm with a clamping jaw. The size of the jaw depends on the inner diameter of the matching upsetting plate to facilitate the subsequent operation of the machine. The excess clamp handle is cut by gas, and the upper part of the gas-cut steel ingot is discarded ≥250mm. Figure 4 shown.

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

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

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

[0078] The forging process was smooth, with no surface cracking. The finished product was achieved after four heat treatments. The hardness after final heat treatment was 80-82 HSD (81 ± 1 HSD). Defects in the working layer were ≤ Ø1, and in other areas ≤ Ø3, meeting the requirements of flaw detection standards.

[0079] Example 2

[0080] According to the blank size, weight, select the appropriate steel ingot, the case of 75T electroslag steel ingot forging production, utilization rate of 71%. The specific information of the material: C 0.69%, Si 0.50%, Mn 0.60%, P 0.015%, S 0.005%, Cr 5.34%, Ni 0.35%, Mo 0.80%, V 0.15%.

[0081] The first fire: after the ingot according to the special ladder heating curve Figure 6 The first fire: after the ingot according to the special ladder heating curve

[0082] The second fire: the initial forging furnace temperature is 1240±10℃, and the holding time is 40h. After the furnace is discharged, select the appropriate upsetting disc, place the blank between the upsetting disc and the upsetting cover plate, put the tongs in the hole of the upsetting disc, and upset to H=1900mm.

[0083] The third fire: the initial forging furnace temperature is 1240±10℃, and the holding time is 40h. After the furnace is discharged, KD is elongated to Φ1450mm, full anvil feeding, after one pass is pressed, it is turned over 90° and half anvil is pressed, the total pass is 10 passes.

[0084] The fourth fire: the initial forging furnace temperature is 1210±10℃, and the holding time is 10h. After the furnace is discharged, the upper flat and V anvil are elongated to Φ1250mm, the weight of the roll neck is discharged, the small circles at both ends are elongated to the blank size, the excess length is gas cut, and the finished product is discharged.

[0085] The forging process is smooth, and the finished product is discharged after four fires. After the final heat treatment, the hardness is 81-83HSD (82±1). The working layer defect equivalent is ≤Φ2, and the defect equivalent of other areas is ≤Φ3, which meets the requirements of the flaw detection standard.

[0086] Example 3

[0087] According to the blank size, weight, select the appropriate steel ingot, the case of 75T electroslag steel ingot forging production, utilization rate of 71%. The specific information of the material: C 0.69%, Si 0.50%, Mn 0.60%, P 0.015%, S 0.005%, Cr 5.34%, Ni 0.35%, Mo 0.80%, V 0.15%.

[0088] The first fire: after the ingot according to the special ladder heating curve Figure 7The pre-forging heating and holding are performed. The KD pre-drawing is elongated to Φ1700mm x 4550mm, the reduction is 20% of the blank height, the bottom of the ingot is pressed by 450mm, the size of the jaw is determined by the inner hole diameter of the matched upsetting die, and the subsequent operation machine is clamped conveniently. The excess jaw handle is gas cut, and the upper scrap of the ingot is gas cut to be greater than or equal to 250mm.

[0089] The second forging: the initial forging temperature is 1230±10℃, the holding time is 50h, and the ingot is selected to be placed between the upsetting die and the upsetting cover plate, the jaw is placed in the inner hole of the upsetting die, and the upsetting is performed to H=1950mm.

[0090] The third forging: the initial forging temperature is 1230±10℃, the holding time is 50h, the KD is elongated to Φ1500mm, the full anvil is fed, the anvil is turned by 90° after one pass is pressed, the total pass is 10 passes.

[0091] The fourth forging: the initial forging temperature is 1200±10℃, the holding time is 15h, the upper flat and lower V anvil is elongated to Φ1300mm, the blank is discharged according to the required weight of the roll neck, the roll neck is elongated to a diameter of Φ1000mm, and the ingot is returned to be heated.

[0092] The fifth forging: the initial forging temperature is 1170±10℃, the holding time is 7h, the upper flat and lower V anvil is elongated to the blank size, and the finished product is discharged.

[0093] There is no cracking phenomenon in the forging process, the production process is smooth, and the finished product is discharged after five forgings. After the final heat treatment, the hardness is 82-84HSD (83±1). The working layer defect equivalent is less than or equal to Φ2, and the defect equivalent of other areas is less than or equal to Φ4, which meets the requirements of the flaw detection standard.

[0094] Comparative Example 1

[0095] The appropriate ingot is selected according to the blank size and weight, the 83T vacuum smelting top pouring ingot is used for forging production in the case, and the utilization rate is 60.1%. The specific information of the material is as follows: C 0.65%, Si 0.55%, Mn 0.65%, P 0.015%, S 0.005%, Cr 5.10%, Ni 0.40%, Mo 0.75%, and V 0.15%.

[0096] The first forging: the ingot is directly placed into the heating furnace after being taken out, heated to 1250℃, and held for 10h before being discharged. The jaw is pressed, the bottom of the ingot water hole is gas cut, and the excess jaw handle is gas cut.

[0097] The second forging: the initial forging temperature is 1250±10℃, the holding time is 22h, the ingot is selected to be placed between the upsetting die and the upsetting cover plate, the jaw is placed in the inner hole of the upsetting die, and the upsetting is performed to H=1850mm.

[0098] Third fire: the initial forging furnace temperature is 1250±10℃, the holding time is 22h, the KD elongation is to Φ1400mm after the furnace is discharged, the full anvil feeding is performed, the total pass is 10 after the first pass is completed and the anvil is turned over by 90°, and the second pass is pressed.

[0099] Fourth fire: the initial forging furnace temperature is 1220±10℃, the holding time is 10h, the elongation is to Φ1200mm after the furnace is discharged, the blank size is obtained by elongating the small circles at both ends according to the required weight of the roll neck, the excess length is cut by gas cutting, and the finished product is discharged.

[0100] Fifth fire: the initial forging furnace temperature is 1190±10℃, the holding time is 7h, the elongation is to the blank size after the furnace is discharged, and the finished product is discharged.

[0101] The double vacuum ingot is selected, no pre-elongation process is performed, the holding time before the upsetting and KD elongation is not considered as the homogenization time. The surface of the double vacuum ingot is easy to crack, the longitudinal cracks are generated on the surface in the upsetting fire, and the cleaning process is added. The homogenization time is not considered, the hardness is 80-85HSD after the final heat treatment, the uniformity is ±2.5HSD, the working layer defect equivalent is ≤Φ2, the defect equivalent in other areas is ≤Φ8, and the core quality does not meet the requirements of the flaw detection standard.

[0102] Comparative Example 2

[0103] The appropriate ingot is selected according to the blank size and weight, the 80T vacuum smelting top pouring ingot is used for forging production in the case, and the utilization rate is 62%. The specific information of the material is as follows: C 0.65%, Si 0.55%, Mn 0.65%, P 0.015%, S 0.005%, Cr 5.10%, Ni 0.40%, Mo 0.75%, and V 0.15%.

[0104] First fire: the ingot is directly placed into the heating furnace after being taken out, heated to 1250℃, and discharged after holding for 50h. The tongs are pressed, and the pre-elongation is to Φ1700mm×4550mm. The bottom of the ingot water gap is cut by gas cutting, and the excess tongs are discarded.

[0105] Second fire: the initial forging furnace temperature is 1250±10℃, the holding time is 20h, the appropriate upsetting leak plate is selected after the furnace is discharged, the blank is placed between the upsetting leak plate and the upsetting cover plate, the tongs are placed in the hole of the upsetting leak plate, and the upsetting is to H=1850mm.

[0106] Third fire: the initial forging furnace temperature is 1250±10℃, the holding time is 20h, the KD elongation is to Φ1400mm after the furnace is discharged, the full anvil feeding is performed, the total pass is 10 after the first pass is completed and the anvil is turned over by 90°, and the second pass is pressed.

[0107] The fourth fire: the initial forging furnace temperature is 1220±10℃, the temperature is kept for 10 hours, the Φ1200mm is pulled up from the upper flat and the V anvil, the weight of the roll neck is discharged, the small circle at two ends is pulled up to the blank size, the excess length is cut by the air, and the finished product is discharged.

[0108] The fifth fire: the initial forging furnace temperature is 1190±10℃, the temperature is kept for 7 hours, the roll neck is pulled up from the upper flat and the V anvil to the blank size, and the finished product is discharged.

[0109] The double vacuum ingot is selected for the steel ingot, the homogenization time is not considered in the first fire heating, the pre-pulling, upsetting and KD pulling, and the homogenization time is not considered in the holding time, so that the diffusion effect of the core is not good. After the final heat treatment, the hardness is 80-84HSD, the uniformity is ±2HSD, the working layer defect equivalent is ≤Φ2, the defect equivalent of other areas is ≤Φ6, and the core quality does not meet the flaw detection standard requirements.

[0110] In summary, the large aluminum plate rolling mill working roll product provided by the application has a dense core structure, the as-cast defects are fully improved, the surface purity is high, the SN322-11 flaw detection standard is met, the structure is uniform, the hardness uniformity reaches ±1HSD, the total amount of carbide in the structure is increased, the carbide type is changed, the hardenability is improved, the hardness reaches ≥80HSD, and the wear resistance and the anti-peeling property of the product are improved.

[0111] The above is only the preferred specific embodiment of the application, but the protection scope of the application is not limited to this, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the application, which should be covered in the protection scope of the application.

Claims

1. A forging method of a work roll for a large aluminum sheet rolling mill, characterized by, The forging method specifically comprises the following steps: S1 first fire: using a step heating curve to heat treat the steel ingot, after the heat treatment, using KD pre-drawing of upper and lower V-shaped anvil to draw out; the bottom of the steel ingot is pressed to open the mouth, and the excess mouth is cut off by air cutting according to the tonnage of the steel ingot; the upper part of the steel ingot is cut off by air cutting; S2 second fire: after the steel ingot is heated at temperature T3 for a certain time, the holding time is determined according to 2-4h per 100mm of the diameter of the steel ingot after KD pre-drawing of the first fire, the steel ingot is drawn out using upsetting disc and spherical upsetting cover plate according to the upsetting ratio of 1.5-2.5 to be upset to the process required height; S3 third fire: after the steel ingot is heated at temperature T3 for a certain time, the holding time is determined according to 2-4h per 100mm of the diameter of the steel ingot after upsetting of the second fire, the steel ingot is drawn out using upper and lower V-shaped anvil according to the KD drawing ratio of 2.0-2.5 to be drawn to the process required diameter; S4 fourth fire: after the steel ingot is heated at temperature T4 for a certain time, the holding time is determined according to 30-60min per 100mm of the diameter of the steel ingot after KD drawing of the third fire; the steel ingot is drawn out using upper flat anvil and lower V-shaped anvil to the diameter of the blank drawing, and the roll neck is cut out according to the process required length at both ends of the blank water head, and the finished product is drawn out; Wherein T3 is in the range of 1200-1250℃, and T4 < T3.

2. The forging method according to claim 1, characterized by, The steel ingot is a high-carbon 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% according to the percentage of mass.

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

4. The forging method according to claim 1, characterized by, In S1, the step heating curve is specifically: The first stage: heat the steel ingot to temperature T1 and hold for a period of time h1, wherein T1 is the temperature of the steel ingot when it is ingot, and h1 is 30-60min per 100mm of the diameter of the steel ingot; The second stage: heat the steel ingot to temperature T2 and hold for a period of time h2, wherein T2 is the complete transformation temperature of austenite, which is in the range of 780-880℃, h2 is 30-60min per 100mm of the diameter of the steel ingot, and the heating rate is ≤50℃ / h; The third stage: heat the steel ingot to temperature T3 and hold for a period of time h3, wherein T3 is the initial forging temperature, which is in the range of 1200-1250℃, and h3 is 30-60min per 100mm of the diameter of the steel ingot.

5. The forging method of claim 1 wherein, The total forging ratio of the forging method is ≥4.5, the initial forging temperature is 1200-1250℃, and the final forging temperature of each fire is ≥850℃.

6. The forging method of claim 1, wherein The temperature T4 and T3 satisfy: T4 = T3-30℃.

7. The forging method of claim 1 wherein, If the fourth fire of step S4 fails to complete the finished product, step S5 fifth fire is performed: The ingot is heated at a starting forging temperature T5 for a certain time, the holding time is determined according to 30-60 min per 100 mm of the diameter of the neck of the ingot, and the ingot is continuously elongated using an upper flat anvil and a lower V anvil until a finished product is obtained; The starting forging temperatures T5 and T4 satisfy T5=T4-30℃.

8. The forging method of claim 1 wherein, In the step S3, the specific operation is that during the elongation, after one pass is completed, the anvil is turned over by 90°, the next pass is pressed, and the total number of passes is 8-12.

9. The forging method of claim 1 wherein, In the step S4, the neck of the ingot is cut out, and the finished product is elongated, the specific operation being that the small circles at both ends are sequentially elongated from the middle to both ends to the size of each step, the excess length is cut by gas cutting, and the finished product is obtained.

10. A large aluminum sheet rolling mill work roll characterized by, The work roll is prepared by the forging method in any one of claims 1-9, satisfies the SN322-11 flaw detection standard, has a hardness of ≥80HSD, and has a hardness uniformity of ±1HSD.

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