Radial forging and ring rolling cooperation forming process for guide wheel rim

Abstract

The application discloses a radial forging and rolling ring cooperation forming process of a guide wheel rim, belongs to the technical field of metal plastic forming, and aims at the problems of large axial expansion and insufficient filling of a complex section during rolling ring of an existing uniform wall thickness ring blank, and the application first performs radial forging on the ring blank, applies unequal reduction along the axial partition, forms a wall thickness gradient preformed blank positively correlated with the target section volume distribution, then establishes a temperature difference field with the thick area higher than the thin area, and performs rolling ring diameter expansion under the surface constraint of the main roller flow limiting flange, filling concave cavity and core roller avoiding groove, so that the thick area metal preferentially fills the complex section in the circumferential direction, and the thin area inhibits the axial expansion. The process can improve the material utilization rate to more than 85%, the complex section filling qualified rate is greater than or equal to 98%, and the axial expansion amount is less than or equal to 2%, and is used for near net shape forming and manufacturing of the guide wheel rim of engineering machinery.

Description

Technical Field

[0001] This invention relates to the field of metal plastic forming technology, and in particular to a radial forging and rolling process for guide wheel rims. Background Technology

[0002] The idler wheel is a key load-bearing component of the tracked construction machinery's walking system. During operation, its rim bears complex alternating stresses with radial loads of 50–300 kN, linear velocities of 0.5–3 m / s, and ambient temperatures ranging from -40℃ to 80℃, and is subjected to strong abrasive wear. The rim's cross-section typically exhibits non-uniform wall thickness characteristics, including the tread's main load-bearing area, the sidewall transition area, and the rim boss area. The tread's main load-bearing area directly bears the load and contacts the track tracks, resulting in a thicker wall. The rim boss area is used for axial restraint and has a complex cross-sectional profile. The sidewall transition area connects the tread and the rim boss, and has a relatively thinner wall.

[0003] Currently, there are three main manufacturing processes for guide wheel rims.

[0004] The first method is casting, which involves pouring molten steel into the casting. This method has a high material utilization rate, but the casting is prone to defects such as shrinkage porosity, gas pores, and coarse grains. Shrinkage porosity defects are particularly difficult to completely eliminate in thick-walled sections, resulting in low fatigue strength. The wheel rim is prone to fatigue cracking under heavy-load alternating stress conditions, making it difficult to meet the requirements for long service life.

[0005] The second method is free forging and machining, which involves free forging a billet and then machining away excess metal to obtain the final cross-sectional shape. This method has low material utilization, typically only 40% to 50%; long processing cycle, with a single piece typically taking 6 to 10 hours or more; and the metal flow lines are interrupted during machining, especially in the transition area between the tread and the sidewall, leading to stress concentration at the abrupt change in cross-section, impaired fatigue performance, and wheel rim fatigue life generally below the design requirement of 80%.

[0006] The third method is the uniform wall thickness ring rolling process, which involves first preparing a ring blank with uniform wall thickness, and then expanding it through rolling. Because the axial wall thickness of the ring blank is uniform, during the rolling process, the metal thins radially while primarily widening axially. Complex cross-sectional features (such as bosses, grooves, and steps) are difficult to fill completely, easily leading to defects such as folds, missing material, and incomplete contours. For guide wheel rims with rim bosses, the scrap rate due to insufficient boss filling is typically between 5% and 10%. Simply increasing the blank volume to ensure filling further increases the axial widening, resulting in material waste and excessive machining allowances. Machining allowances typically need to reach 5–8 mm per side, and folding defects at the boss root are difficult to completely remove through subsequent machining.

[0007] In existing technologies, although radial forging is used for billet preparation and subsequent ring rolling, the radial forging stage is typically only used for uniform wall reduction or simple shaping. It does not involve axial differential pre-allocation of volume distribution for the final forging cross-section, nor does it coordinate with the temperature field, deformation, transfer time, and die profile of the ring rolling stage. Specifically, the preformed billet after uniform wall reduction still suffers from the same axial widening problem as the uniform wall thickness ring billet during the ring rolling stage; while the simple shaping process only improves surface quality and cannot solve the fundamental contradiction of insufficient filling of complex cross-sections.

[0008] Therefore, none of the existing processes mentioned above can simultaneously meet the three core requirements of high material utilization, complete cross-sectional filling, and long fatigue life. In the mass production of guide wheel rims for engineering machinery, there is an urgent need for a near-net-shape forming process that can accurately pre-allocate the metal volume axially before ring rolling and control the metal flow direction through temperature field and profile constraints during the ring rolling stage. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a radial forging and rolling process for guide wheel rims. It aims to solve the contradiction between the axial widening of metal and the insufficient filling of complex cross sections during the rolling of uniform wall thickness ring blanks in the existing guide wheel rim manufacturing process, as well as the problems of internal defects and low fatigue life caused by the casting process.

[0010] To achieve the aforementioned objectives, the first aspect of this invention proposes a radial forging and rolling process for the guide wheel rim, comprising the following steps: S1. Billet preparation: Select medium carbon microalloyed steel, heat to 1150~1250℃ and hold for 2~4 hours to obtain ring billet; S2. Radial Forging with Unequal Axial Section Reduction: The annular blank is fitted onto the radial forging press mandrel, and the annular blank is radially forged using multiple section hammers with independently controllable axial reduction. Based on the required filling volume of each characteristic area of ​​the target guide wheel rim cross-section, different radial reductions are applied to each section, causing the preformed blank to form a wall thickness gradient distribution positively correlated with the target cross-sectional volume distribution. The wall thickness ratio of the thick section to the thin section is controlled between 1.2 and 2.5, and the total radial compression is controlled between 25% and 45%. S3. Temperature difference field establishment and transfer: The temperature of the preform obtained in step S2 is controlled so that the temperature of the thick area is higher than that of the thin area, forming a temperature difference field with a thick area temperature of 950-1000℃, a thin area temperature of 850-900℃, and a temperature difference of ≥80℃ and ≤200℃; the preform is transferred to the ring rolling mill within 20-40 seconds. S4. Circumferential Filling for Ring Expansion: The preformed billet is fitted onto the core roll of the ring rolling mill, and the main roll expands the ring diameter by radial feeding. The main roll profile is provided with a flow-limiting flange and a filling cavity that are complementary to the outer contour of the target wheel rim, and the core roll profile is provided with a clearance groove. During the ring rolling process, the thick metal preferentially flows circumferentially to fill the complex cross section under the action of triaxial compressive stress, while the thin area forms an axial flow resistance barrier to inhibit axial widening. The total radial compression of the ring is 25% to 45%, the expansion ratio is 1.2 to 1.8, and the final rolling temperature is ≥750℃.

[0011] Optionally, in step S2, the annular blank is divided into at least three characteristic zones along the axial direction: the tread main load-bearing zone, the sidewall transition zone, and the rim boss zone; the required filling volume Vi for each characteristic zone is obtained by integrating the target cross-sectional profile; the volume retention weight Wi for each zone is calculated using the following formula: Wi=α×(Vi / Vtotal)^β+γ×(Ti / Tref)^δ+η×(σsi / σsref) In the formula: Vi is the characteristic volume of the target section of the i-th partition; Vtotal is the sum of the characteristic volumes of the target sections of all partitions; Ti is the radial forging temperature of the i-th partition; Tref is the reference temperature, taken as 1150℃; σsi is the flow stress of the material in the i-th partition under Ti; σsref is the reference flow stress; α=0.45~0.65, γ=0.20~0.35, η=0.15~0.25, and α+γ+η=1; β=1.2~1.8, δ=0.5~1.0; Normalization is performed using Wi' = Wi / ΣWi, where ΣWi is the weighted sum of the volumes of all partitions; the target wall thickness hi of each partition is determined by the following formula: hi=havg+λ×havg×(Wi'-1 / n) In the formula: havg is the target average wall thickness; n is the number of axial partitions; λ is the wall thickness gradient coefficient, with a value ranging from 0.2 to 0.8; The radial reduction of each section is Δhi = H0 - hi, where H0 is the initial wall thickness.

[0012] Optionally, in step S2, a nonlinear transition section is provided between adjacent sections of the preform, and the wall thickness of the transition section is determined by the following formula: h(z)=hi+(hi+1-hi)×f((z-zi) / Lt) In the formula, z is the axial coordinate; zi is the axial coordinate at the boundary between the i-th partition and the (i+1)-th partition; f(x) = 3x 2 -2x 3 The transition section length Lt ≥ 3|hi+1-hi|; the transition fillet radius ≥ 1.5|hi+1-hi|.

[0013] Optionally, in step S4, the feed speed v of the rolling ring is dynamically adjusted based on the measured temperature difference and axial widening rate, and the adjustment formula is: v=v0×ΔT_actual / ΔTref×[1-k1×(ΔT_actual-ΔTmin) / ΔTmin-k2×(B_dot-εmax) / εmax] In the formula: ΔT_actual is the measured temperature difference between the thick and thin regions; v0 is the reference feed rate, which is 0.5 to 3.0 mm / s; ΔTref is the reference temperature difference, which is 150℃; ΔTmin is the minimum allowable temperature difference, which is 80℃; εmax is the maximum allowable axial widening rate, which is 0.5 mm / s; B_dot is the measured axial widening rate; k1 and k2 are the feedback gains, with k1 ranging from 0.2 to 0.5 and k2 ranging from 0.3 to 0.8.

[0014] Optionally, the method also includes step S5, online detection and feedback correction: During or after the ring rolling process, the profile of the wheel rim section is measured online using a laser profile scanner to obtain the deviation ΔVi between the actual filling volume and the target filling volume of each feature area. The feedback control unit then updates the wall thickness gradient coefficient λ and the target wall thickness of each zone in step S2 using the following formula: λnew=λold+κ×Σ|ΔVi| / Vtotal hi_new=hi+κ×ΔVi / (π×Dm×Li) In the formula: κ is the closed-loop gain, which is taken as 0.05 to 0.3; Dm is the average diameter of the preform; and Li is the axial length of the i-th partition.

[0015] Optionally, it also includes abnormal working condition handling steps: when the temperature difference between the thick and thin areas is less than 80°C, extend the dwell time in the heat preservation channel or start the local induction heating device; when the temperature difference is greater than 200°C, start the forced air cooling of the thin area and speed up the transfer speed; when the radial force of the main roller exceeds 120% of the preset value or the axial widening rate exceeds 0.5 mm / s, reduce the feed speed to 0.1 mm / s and increase the pressure of the axial limit roller; if the radial force continues to rise, stop the feed and keep it idling.

[0016] Optionally, in step S3, the temperature difference field is formed by controlling the forced air cooling of the thin area and supplementing the heating of the thick area with a local induction heating device.

[0017] Optionally, in step S2, the wall thickness of the preform is measured in real time using a laser profile scanner, and the pressing amount of each partition hammer is dynamically corrected by the partition pressing control unit to control the wall thickness deviation within ±0.5mm.

[0018] Optionally, in step S4, the axial widening rate and the radial force of the main roll are monitored in real time using a radial force sensor and a laser profile scanner, and the feed speed is dynamically adjusted by a feed servo system; when the axial widening rate exceeds 0.4 mm / s, the feed speed is automatically reduced and the pressure of the axial limit roll is increased.

[0019] Optionally, the medium carbon microalloyed steel is 42CrMo steel or 40Mn2V steel; the process also includes step S6, post-processing: isothermal normalizing or quenching and tempering the wheel rim after ring rolling, with a finishing allowance of 1-2 mm on each side.

[0020] The beneficial effects of this invention are: 1. The radial forging and rolling process of the guide wheel rim of the present invention achieves axial pre-distribution of metal volume through the radial forging stage, so that the cross-sectional profile of the forging after rolling is close to the finished product shape. The single-sided machining allowance is reduced from 5-8mm in the uniform wall thickness ring blank rolling process to 1-2mm, and the material utilization rate is increased from 45%-60% to more than 85%.

[0021] 2. The radial forging and rolling process for the guide wheel rim of this invention, due to the use of radial forging and rolling, ensures that the metal flow lines are continuously distributed along the rim cross-section. This avoids fatigue crack initiation caused by internal defects such as shrinkage porosity and gas holes in the casting process, and also avoids stress concentration caused by the interruption of flow lines at abrupt changes in cross-section in free forging and machining processes. The fatigue life of the rim is 2 to 3 times higher than that of cast rims, and more than 1.5 times higher than that of free forged and machined rims.

[0022] 3. The radial forging and rolling process of the guide wheel rim of the present invention, through the synergistic effect of wall thickness gradient, differential temperature field, and profile constraint, allows the thick metal to preferentially flow circumferentially to fill the complex cross-section under the action of the differential temperature field, while the thin area forms an axial flow resistance barrier to suppress axial widening. The filling qualification rate of the complex cross-section is ≥98%, the axial widening is ≤2%, and the folding defect rate is ≤0.5%.

[0023] 4. The radial forging and rolling process of the guide wheel rim of the present invention improves material utilization and significantly reduces machining allowance, thereby reducing raw material consumption and shortening machining time, which helps to reduce the overall energy consumption of a single piece and shorten the production cycle. Attached Figure Description

[0024] Figure 1 This is an overall flow chart of the radial forging and rolling process of the guide wheel rim in this invention. Figure 2 This is a schematic diagram of the temperature control module and transfer path in this invention; Figure 3 This is a schematic diagram of the structure of the ring forming module in this invention; Figure 4 This is a schematic diagram of the axial wall thickness distribution of the preformed blank in this invention; Figure 5 This is a block diagram of the online detection feedback module and closed-loop control logic in this invention.

[0025] Explanation of reference numerals in the attached figures: 100. Radial forging module; 160. Preformed billet; 200. Temperature control module; 210. Insulation channel; 220. Infrared thermal imager; 230. Local induction heating device; 300. Ring forming module; 310. Main roller; 311. Main roller flow-limiting flange; 312. Main roller filling cavity; 320. Core roller; 321. Core roller clearance groove; 330. Guide roller; 340. Axial limiting roller; 350. Feed servo system; 400. Online detection feedback module; 410. Laser profile scanner; 420. Radial force sensor; 430. Feedback control unit; 440. Abnormal alarm device; 500. Finished guide wheel rim.

[0026] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0029] See Figures 1 to 5 As shown, the radial forging and ring rolling co-forming process of the guide wheel rim of the present invention is completed collaboratively by four functional modules: radial forging module 100, temperature control module 200, ring rolling forming module 300, and online detection feedback module 400. Radial forging module 100 performs axial partitioning and unequal pressing of the annular blank to form a pre-formed blank 160 with a gradient wall thickness distribution; temperature control module 200 establishes and maintains a temperature difference field where the temperature of the thicker area is higher than that of the thinner area during the transfer of the pre-formed blank 160 to the ring rolling mill; ring rolling forming module 300 utilizes the temperature difference field and surface constraints to complete the diameter expansion and filling, achieving near-net-shape forming of the wheel rim; online detection feedback module 400 performs online measurement of the ring rolling results and feeds back the deviation to radial forging module 100, realizing piece-by-piece closed-loop correction.

[0030] The following embodiments use guide wheel rims of different materials and specifications as implementation objects to provide a detailed description of the specific parameters and implementation process of the above process steps.

[0031] Example 1 This embodiment uses 42CrMo steel as raw material to manufacture a guide wheel rim with an outer diameter of 300mm, a tread wall thickness of 20mm, and a rim boss height of 15mm. This specification of rim is used as the guide wheel for the travel system of a medium-sized crawler excavator.

[0032] Step 1: Raw material preparation; 42CrMo steel billets were heated to 1180℃ and held for 3 hours to form annular billets with an outer diameter of 250mm, a wall thickness of 30mm, a height of 80mm, and an inner diameter of 190mm. Heating was carried out in a natural gas regenerative furnace using a three-stage heating process: a preheating stage at 600–800℃ for 0.5 hours, a heating stage at 150℃ / h to 1180℃, and a holding stage at 1180℃ for 3 hours. After the holding period, the temperature difference between the inner and outer walls of the annular billet was controlled within ±10℃ to ensure uniform billet temperature.

[0033] Step 2: Radial forging with unequal axial compression in different zones; The annular blank is fitted onto the mandrel of the radial forging press, with the outer diameter of the mandrel matching the inner diameter of the annular blank, using a clearance fit of 0.5–1 mm. An axial positioning block positions the annular blank axially, ensuring strict alignment between the hammers in each section and the axial sections of the annular blank. The radial forging press employs a four-hammer structure, with the four hammers evenly distributed at 90° angles along the circumference of the annular blank. Each hammer is axially divided into five independently controllable sections, with adjacent sections connected by dovetail joints allowing relative sliding. Each section hammer is driven by an independent hydraulic cylinder.

[0034] Based on the cross-sectional characteristics of the target wheel rim, the annular blank is divided into five characteristic zones along the axial direction: the tread main load-bearing zone (zones 1 and 5, symmetrically distributed at both ends of the axial direction), the sidewall transition zone (zones 2 and 4), and the rim boss zone (zone 3, located in the middle of the axial direction). The target filling volume of each characteristic zone is obtained by integrating the target cross-sectional profile: V1 = V5 = 120 cm. 3 V2=V4=60cm 3 V3 = 180cm 3 .

[0035] Before radial forging, the annular billet undergoes axial zone temperature control, with zones 1 and 5 at 1180℃, zones 2 and 4 at 1080℃, and zone 3 at 1220℃; corresponding to material flow stresses of 55MPa, 75MPa, and 50MPa, respectively. The flow stress at a reference temperature of 1150℃ is 60MPa. Weighting function parameters are set as follows: α=0.55, γ=0.25, η=0.20, β=1.5, δ=0.8. Substituting the volume, temperature, and flow stress of each zone into the weighting formula for calculation, and combining this with trial production iterations, the target wall thicknesses for each zone are obtained: h1=h5=20.5mm, h2=h4=17.5mm, h3=24.0mm. The wall thickness ratio between the thick zone (zone 3) and the thin zone (zones 2 and 4) is 24.0 / 17.5=1.37, satisfying the requirement of a wall thickness ratio of 1.2 to 2.5. The target average wall thickness is 20 mm.

[0036] Radial compression in each zone: Zones 1 and 5: Δh = 30 - 20.5 = 9.5 mm; Zones 2 and 4: Δh = 30 - 17.5 = 12.5 mm; Zone 3: Δh = 30 - 24.0 = 6.0 mm. The total radial compression is (30 - 20) / 30 × 100% ≈ 33.3%, which meets the requirement of 25% to 45%.

[0037] A non-linear transition section is set between adjacent zones. Taking the transition section between zone 2 (h2=17.5mm) and zone 3 (h3=24.0mm) as an example, the transition section length Lt=4×|24.0-17.5|=26mm, satisfying Lt≥3|hi+1-hi|; the transition fillet radius R=2×|24.0-17.5|=13mm, satisfying R≥1.5|hi+1-hi|. The transition section wall thickness is determined by h(z)=hi+(hi+1-hi)×f((z-zi) / Lt), where f(x)=3x 2 -2x 3 .

[0038] The radial forging starts at 1100℃ and ends at 920℃. During the forging process, a laser profile scanner 410 measures the wall thickness of the preform 160 in real time, and the zoned pressing control unit dynamically corrects the pressing amount of the hammers in each zone, keeping the wall thickness deviation within ±0.5mm. After radial forging, the inner diameter of the preform 160 remains constant at 190mm, the outer diameter is 230mm, and the wall thickness along the axial direction shows a gradient distribution: 20.5mm in zones 1 and 5, 17.5mm in zones 2 and 4, and 24.0mm in zone 3.

[0039] Step 3: Establishment and transfer of the temperature difference field; After radial forging, the preform 160 enters the heat preservation channel 210 of the temperature control module 200. The heat preservation channel 210 is a conveyor roller with a heat preservation cover, and the conveying speed is 0.8 m / s. During the conveying process of the preform 160 in the heat preservation channel 210, the thick area (zone 3) has a relatively slow heat dissipation rate due to its wall thickness of 24.0 mm, large heat capacity, and small specific surface area; while the thin areas (zones 2 and 4) have a relatively fast heat dissipation rate due to their wall thickness of 17.5 mm, small heat capacity, and large specific surface area, thus naturally forming an initial temperature difference.

[0040] Based on this, the thin areas (zones 2 and 4) are subjected to controllable forced air cooling, with an air outlet temperature of 80℃, an air velocity of 15m / s, and a cooling time of 10 seconds. The thick area (zone 3) is heated using a local induction heating device 230, with an induction coil frequency of 8kHz, a power of 50kW, and a heating time of 8 seconds. An infrared thermal imager 220 monitors the surface temperature of the preform 160 online, and the feedback signal controls the forced air cooling airflow and induction heating power, creating a temperature difference field of 980℃ for the thick area, 900℃ for the thin area, and a temperature difference of 80℃ on the preform 160 before transfer. The transfer time is controlled at 25 seconds, meeting the requirement of 20–40 seconds.

[0041] Step 4: Circumferential filling for ring enlargement; The preform 160 is fitted onto the core roller 320 of the ring rolling mill. The core roller 320 has a core roller clearance groove 321 on its profile. The position and shape of the core roller clearance groove 321 correspond to the inner contour of the target wheel rim flange boss. The main roller 310 has a main roller flow limiting flange 311 and a main roller filling cavity 312 on its profile. The main roller flow limiting flange 311 is located at both ends of the main roller 310 in the axial direction and cooperates with the axial end face of the core roller 320 to form an axial limit. The main roller filling cavity 312 is located in the middle of the main roller 310 in the axial direction and complements the outer contour of the target wheel rim flange boss.

[0042] Initial rolling temperature of the ring: 950℃ for thick sections and 880℃ for thin sections. The main roll 310 is fed radially at an initial feed speed of 1.5 mm / s, with a total radial compression of 30%, an expansion ratio of 1.30, and a final rolling temperature of 780℃.

[0043] During the ring rolling process, the radial force of the main roller 310 acts on the outer surface of the preform 160, while the core roller 320 provides inner surface support. The preform 160 forms a triaxial compressive stress state between the main roller 310 and the core roller 320. The thicker area has a higher metal temperature and lower flow stress, and under the action of triaxial compressive stress, it preferentially undergoes plastic flow along the circumference, filling the rim boss area corresponding to the main roller filling cavity 312 and the core roller avoidance groove 321. The thinner area has a lower metal temperature and higher flow stress, and is constrained by the main roller flow-limiting flange 311 and the axial end face of the core roller 320. Axial flow is hindered, forming an axial rigid barrier and suppressing axial widening. The guide roller 330 is disposed on the outer periphery of the preform 160, located on both sides of the feed direction of the main roller 310. It can move outward as the diameter of the preform 160 expands, applying radial guiding constraints to the preform 160. This ensures that the preform 160 maintains a stable center position during the ring rolling and diameter expansion process, preventing ring swaying or ellipticization caused by the radial feed of the main roller 310 and the circumferential flow of metal. The axis of the guide roller 330 is parallel to the axis of the main roller 310 and the axis of the core roller 320. The three rollers together form circumferential support for the preform 160, thereby ensuring that the radial compression is evenly distributed along the circumference. This facilitates the uniform filling of the main roller filling cavity 312 and the core roller avoidance groove 321 by thick metal along the circumference, improving the consistency of cross-sectional filling.

[0044] The working principle of this embodiment is as follows: In the radial forging stage, differentiated radial reduction is applied to different axial zones of the ring billet, resulting in selective axial distribution of metal volume. Thicker wall regions have more metal volume available for circumferential filling during the ring rolling stage; thinner wall regions experience higher flow stress under the influence of the differential temperature field, exhibiting stronger resistance to axial widening. During the ring rolling stage, the differential temperature field causes the thicker metal regions to preferentially enter a plastic flow state, while the profile constraints (the main roll flow-limiting flange and the main roll filling cavity) provide a clear circumferential flow channel for the thicker metal regions. The synergistic effect of these three factors achieves a deformation mode of "thick regions circumferentially filling complex cross-sections, and thin regions axially confining," fundamentally resolving the contradiction of insufficient filling of complex cross-sections caused by the free axial widening of metal during the ring rolling of uniformly thick wall billets.

[0045] After the rim is rolled, the rim cross-section is complete, and the main load-bearing area of ​​the tread, the transition area of ​​the side wall, and the rim boss area are all fully filled without defects such as folds, missing material, or missing contours.

[0046] Step 5: Online detection and feedback correction; After the ring rolling is completed, the laser profile scanner 410 performs online measurement of the wheel rim cross-sectional profile to obtain the deviation ΔVi between the actual filling volume and the target filling volume of each feature area. The feedback control unit 430 updates the wall thickness gradient coefficient λ and the target wall thickness of each zone during the radial forging stage according to the following formula: λnew=λold+κ×Σ|ΔVi| / Vtotal hi_new=hi+κ×ΔVi / (π×Dm×Li) In the formula, the closed-loop gain κ is taken as 0.15, Dm is the average diameter of the preformed billet (230 mm), and Li is the axial length of the i-th partition. The updated target wall thickness of each partition is used for radial forging control of the next preformed billet, realizing piece-by-piece closed-loop correction.

[0047] Step Six: Follow-up Processing; The finished guide wheel rim (500mm) after ring rolling undergoes isothermal normalizing treatment at 860℃, with a holding time calculated based on a wall thickness of 1.5 min / mm. After holding, it is air-cooled to room temperature. Normalizing refines the grains, eliminates forging stress, and yields a uniform pearlite + ferrite microstructure. A finishing allowance of 1.5mm is provided on each side.

[0048] The guide wheel rim produced in this embodiment has a material utilization rate of 88%, a cross-sectional filling qualification rate of 99%, an axial widening of 1.8%, and no folding defects. The rim fatigue life test was conducted according to the standard loading spectrum, and the fatigue life reached 2.8 times that of the cast rim. Compared with the ring rolling process for uniform wall thickness ring blanks of the same specifications, the material utilization rate increased from 55% to 88%, and the single-piece machining time decreased from 6 hours to 2 hours.

[0049] Example 2 This embodiment uses 40Mn2V steel as raw material to manufacture a guide wheel rim with an outer diameter of 350mm, a tread wall thickness of 25mm, and double-sided bosses. This specification of wheel rim is used as the guide wheel of the walking system of a large tracked bulldozer.

[0050] Step 1: Raw material preparation; A 40Mn2V steel billet was heated to 1200℃ and held for 3.5 hours to form an annular billet with an outer diameter of 280mm, a wall thickness of 35mm, and a height of 90mm, and an inner diameter of 210mm. The heating regime was the same as in Example 1, and the temperature difference between the inner and outer walls of the annular billet was controlled within ±12℃ after the holding period.

[0051] Step 2: Radial forging with unequal axial compression in different zones; In this embodiment, since the target wheel rim has double-sided bosses and the cross-section is symmetrically distributed along the axial direction, the annular blank is divided into 7 characteristic areas along the axial direction: three tread main bearing areas at both ends and the middle of the axial direction (areas 1, 4, and 7), two side wall transition areas (areas 2 and 6), and two wheel rim boss areas (areas 3 and 5).

[0052] Before radial forging, the annular billet undergoes axial zone temperature control to ensure different temperatures and flow stresses in each zone. Weighting function parameters are set as follows: α=0.60, γ=0.22, η=0.18, β=1.6, δ=0.7, and wall thickness gradient coefficient λ=0.6. The volume, temperature, and flow stress of each zone are substituted into the weighting formula for calculation. Combined with trial production iterations, the target wall thickness for each zone is determined to be an alternating distribution of thick and thin sections: the thick zone (zones 3 and 5, the rim boss area) has a maximum wall thickness of 32mm, and the thin zone (zones 2 and 6, the sidewall transition area) has a minimum wall thickness of 20mm, with a thickness-to-thin ratio of 1.6, meeting the requirement of a wall thickness ratio of 1.2–2.5. The preformed billet has an average wall thickness of approximately 25mm and a total radial compression of approximately 29%, meeting the requirement of 25%–45%.

[0053] A non-linear transition section is set between adjacent partitions. The length of the transition section is Lt=4×|hi+1-hi|, the radius of the transition fillet is R=2×|hi+1-hi|, and the wall thickness of the transition section is determined by h(z)=hi+(hi+1-hi)×f((z-zi) / Lt).

[0054] During radial forging, the laser profile scanner 410 measures the wall thickness of the preform 160 in real time, and the zone pressing control unit dynamically corrects the pressing amount of each zone hammer, with the wall thickness deviation controlled within ±0.5mm. After radial forging is completed, the inner diameter of the preform 160 remains unchanged at 210mm, and the outer diameter is 260mm.

[0055] Step 3: Establishment and transfer of the temperature difference field; Localized induction heating device 230 provides heating to the thick areas (zones 3 and 5), with an induction coil frequency of 6kHz, a power of 60kW, and a heating time of 12 seconds. Forced air cooling is applied to the thin areas (zones 2, 4, and 6), with an air outlet temperature of 100℃, a wind speed of 18m / s, and a cooling time of 15 seconds. Infrared thermal imager 220 monitors the surface temperature online and uses feedback to control the forced air cooling airflow and induction heating power, creating a temperature difference field with a thick area temperature of 1000℃ and a thin area temperature of 860℃, a temperature difference of 140℃. The transfer time is 30 seconds.

[0056] Step 4: Circumferential filling for ring enlargement; The initial rolling temperature of the ring is 960℃ for the thick section and 840℃ for the thin section. The initial feed speed of the main roll is 2.0 mm / s, the total radial compression is 35%, the diameter expansion ratio is 1.35, and the final rolling temperature is 820℃.

[0057] During the ring rolling process, the online detection feedback module 400 monitors the axial widening rate and the radial force of the main roller in real time. The radial force sensor 420 is installed at the bearing housing of the main roller 310 to measure the radial force of the main roller; the laser profile scanner 410 measures the axial width of the wheel rim in the ring rolling gap and calculates the axial widening rate B_dot. The feed servo system 350 adjusts the feed speed according to the measured data and a dynamic adjustment formula. v=v0×ΔT_actual / ΔTref×[1-k1×(ΔT_actual-ΔTmin) / ΔTmin-k2×(B_dot-εmax) / εmax] In the formula, v0 = 2.0 mm / s, ΔTref = 150℃, ΔTmin = 80℃, εmax = 0.5 mm / s, k1 = 0.3, and k2 = 0.5. When the axial widening rate exceeds 0.4 mm / s, the feed speed automatically decreases to 0.8 mm / s, while the pressure of the axial limit roller 340 is increased by 20%. Through dynamic adjustment, the axial widening rate is always controlled within 0.5 mm / s.

[0058] As the rolling ring expands, the outer diameter of the preform 160 gradually increases from 260mm to 350mm. The guide roller 330 moves radially outward under the drive of the hydraulic follow-up mechanism, always maintaining contact with the outer surface of the preform 160. The contact force is controlled at 10-20kN to avoid excessive radial constraint affecting the expansion flow.

[0059] Step 5: Online detection and feedback correction; A piece-by-piece closed-loop correction strategy was adopted. After each rolling ring was completed, the wall thickness gradient coefficient λ and the target wall thickness of each zone were updated according to the formula in Example 1. The closed-loop gain κ was set to 0.10. After 10 pieces were produced continuously, the wall thickness deviation stabilized within ±0.3mm, and the cross-section filling qualification rate stabilized above 98.5%.

[0060] Step Six: Follow-up Processing; Tempering treatment: oil quenching at 850℃ for 2 hours, followed by tempering at 550℃ for 2 hours and air cooling. Tempered sorbite structure is obtained after tempering treatment, with a hardness of 28–32 HRC. Finishing allowance is 1.2 mm per side.

[0061] The guide wheel rim produced in this embodiment has a material utilization rate of 90%, a cross-sectional filling qualification rate of 98.5%, an axial widening of 1.5%, and a folding defect rate of 0.2%. Fatigue life testing was conducted according to the standard loading spectrum, and the fatigue life reached 2.5 times that of the casting. Compared with the free forging + machining process of the same specifications, the material utilization rate increased from 50% to 90%, and the machining time per piece decreased from 8 hours to 2.5 hours.

[0062] Example 3 This embodiment describes the handling of abnormal operating conditions. The abnormal operating condition handling logic is integrated into the feedback control unit 430, which works in conjunction with the online detection feedback module 400 to ensure process stability during mass production.

[0063] When the infrared thermal imager 220 detects a temperature difference of less than 80°C between the thick and thin areas (i.e., the temperature difference is below the minimum allowable temperature difference ΔTmin), the temperature difference field is insufficient to guide the preferential circumferential flow of metal in the thick area. At this time, the feedback control unit 430 automatically outputs a control signal to extend the dwell time of the heat preservation channel 210 by 5 seconds, allowing the thin area to cool further through natural heat dissipation. If the temperature difference is still less than 80°C after extending the dwell time, the local induction heating device 230 is activated to supplement the heating of the thick area until the temperature difference recovers to above 80°C. After the temperature difference recovers, the preformed billet 160 can then be transferred to the ring rolling mill.

[0064] When the infrared thermal imager 220 detects a temperature difference greater than 200℃, meaning the temperature difference exceeds the upper limit of the process window, the temperature in the thin area may be approaching the brittle range of the material, posing a risk of ring rolling cracking. At this time, the feedback control unit 430 outputs a control signal to activate the power reduction mode of the forced air cooling device in the thin area or shut down the air cooling, while simultaneously shortening the transfer time to less than 20 seconds, ensuring that the preform 160 reaches the ring rolling mill before the temperature in the thin area drops excessively. If the temperature difference is still too large, the induction heating power in the thick area is appropriately reduced to bring the temperature difference back below 200℃.

[0065] When the radial force sensor 420 detects that the radial force of the main roller exceeds 120% of the preset value, it indicates an abnormal increase in the rolling ring resistance, which may indicate obstructed metal flow or abnormal contact of the mold surface. At this time, the feed servo system 350 immediately reduces the feed speed to 0.1 mm / s and increases the pressure of the axial limit roller 340 by 20%, thereby alleviating the radial force overload by reducing the deformation rate and strengthening the axial constraint. If the radial force continues to rise, the feed is stopped and the machine is kept idle for 5 seconds until the radial force decreases, after which the feed is resumed. During the idle period, the preform 160 is only subjected to contact pressure between the main roller 310 and the core roller 320 without further deformation, thus avoiding mold damage and rim cracking caused by the continuous increase in radial force.

[0066] When the laser profile scanner 410 detects a local wall thickness deviation exceeding ±1.0 mm or insufficient cross-sectional filling, the abnormality alarm device 440 issues an audible and visual alarm, marks the part as a defective product, and feeds back the deviation data to the zone pressing control unit of the radial forging module 100 to correct the wall thickness distribution of the next preform 160. The corrected wall thickness data is automatically loaded during the next radial forging, enabling rapid process recovery under abnormal conditions.

[0067] The above-mentioned abnormal operating condition handling mechanism can effectively avoid defects such as cracking, folding, and insufficient filling of the rolling ring, ensuring the stability of mass production and the product qualification rate. In the actual continuous production of 200 pieces in the batch test, after adopting the above-mentioned abnormal operating condition handling mechanism, no batch scrapping accidents caused by fluctuations in process parameters occurred.

[0068] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A radial forging and rolling process for forming a guide wheel rim, characterized in that, Includes the following steps: S1. Billet preparation: Select medium carbon microalloyed steel, heat to 1150~1250℃ and hold for 2~4 hours to obtain ring billet; S2. Radial Forging with Unequal Axial Section Reduction: The annular blank is fitted onto the radial forging press mandrel, and the annular blank is radially forged using multiple section hammers with independently controllable axial reduction. Based on the required filling volume of each characteristic area of ​​the target guide wheel rim cross-section, different radial reductions are applied to each section, causing the preformed blank to form a wall thickness gradient distribution positively correlated with the target cross-sectional volume distribution. The wall thickness ratio of the thick section to the thin section is controlled between 1.2 and 2.5, and the total radial compression is controlled between 25% and 45%. S3. Temperature difference field establishment and transfer: The temperature of the preform obtained in step S2 is controlled so that the temperature of the thick area is higher than that of the thin area, forming a temperature difference field with a thick area temperature of 950-1000℃, a thin area temperature of 850-900℃, and a temperature difference of ≥80℃ and ≤200℃; the preform is transferred to the ring rolling mill within 20-40 seconds. S4. Circumferential Filling for Ring Expansion: The preformed billet is fitted onto the core roll of the ring rolling mill, and the main roll expands the ring diameter by radial feeding. The main roll profile is provided with a flow-limiting flange and a filling cavity that are complementary to the outer contour of the target wheel rim, and the core roll profile is provided with a clearance groove. During the ring rolling process, the thick metal preferentially flows circumferentially to fill the complex cross section under the action of triaxial compressive stress, while the thin area forms an axial flow resistance barrier to inhibit axial widening. The total radial compression of the ring is 25% to 45%, the expansion ratio is 1.2 to 1.8, and the final rolling temperature is ≥750℃.

2. The radial forging and rolling process for the guide wheel rim according to claim 1, characterized in that, In step S2, the annular blank is divided into at least three characteristic zones along the axial direction: the tread main load-bearing zone, the sidewall transition zone, and the rim boss zone; the required filling volume Vi for each characteristic zone is obtained by integrating the target cross-sectional profile; the volume retention weight Wi for each zone is calculated using the following formula: Wi=α×(Vi / Vtotal)^β+γ×(Ti / Tref)^δ+η×(σsi / σsref) In the formula: Vi is the characteristic volume of the target section of the i-th partition; Vtotal is the sum of the characteristic volumes of the target cross-sections of all zones; Ti is the radial forging temperature of the i-th zone; Tref is the reference temperature, taken as 1150℃; σsi is the flow stress of the material in the i-th zone under Ti; σsref is the reference flow stress; α=0.45~0.65, γ=0.20~0.35, η=0.15~0.25, and α+γ+η=1; β=1.2~1.8, δ=0.5~1.0; Normalization is performed using Wi' = Wi / ΣWi, where ΣWi is the weighted sum of the volumes of all partitions; the target wall thickness hi of each partition is determined by the following formula: hi=havg+λ×havg×(Wi'-1 / n) In the formula: havg is the target average wall thickness; n is the number of axial partitions; λ is the wall thickness gradient coefficient, with a value ranging from 0.2 to 0.8; The radial reduction of each section is Δhi = H0 - hi, where H0 is the initial wall thickness.

3. The radial forging and rolling process for the guide wheel rim according to claim 2, characterized in that, In step S2, a nonlinear transition section is set between adjacent sections of the preform, and the wall thickness of the transition section is determined by the following formula: h(z)=hi+(hi+1-hi)×f((z-zi) / Lt) In the formula, z is the axial coordinate; zi is the axial coordinate at the boundary between the i-th partition and the (i+1)-th partition; f(x) = 3x 2 -2x 3 The transition section length Lt ≥ 3|hi+1-hi|; the transition fillet radius ≥ 1.5|hi+1-hi|.

4. The radial forging and rolling process for the guide wheel rim according to claim 2, characterized in that, In step S4, the feed speed v of the rolling ring is dynamically adjusted based on the measured temperature difference and axial widening rate. The adjustment formula is as follows: v=v0×ΔT_actual / ΔTref×[1-k1×(ΔT_actual-ΔTmin) / ΔTmin-k2×(B_dot-εmax) / εmax] In the formula: ΔT_actual is the measured temperature difference between the thick and thin regions; v0 is the reference feed rate, which is 0.5 to 3.0 mm / s; ΔTref is the reference temperature difference, which is 150℃; ΔTmin is the minimum allowable temperature difference, which is 80℃; εmax is the maximum allowable axial widening rate, which is 0.5 mm / s; B_dot is the measured axial widening rate; k1 and k2 are the feedback gains, with k1 ranging from 0.2 to 0.5 and k2 ranging from 0.3 to 0.

8.

5. The radial forging and rolling process for the guide wheel rim according to claim 2, characterized in that, The process also includes step S5, online detection and feedback correction: During or after the ring rolling process, the profile of the wheel rim section is measured online using a laser profile scanner to obtain the deviation ΔVi between the actual filling volume and the target filling volume of each feature area. The feedback control unit then updates the wall thickness gradient coefficient λ and the target wall thickness of each zone in step S2 using the following formula: λnew=λold+κ×Σ|ΔVi| / Vtotal hi_new=hi+κ×ΔVi / (π×Dm×Li) In the formula: κ is the closed-loop gain, which is taken as 0.05 to 0.3; Dm is the average diameter of the preform; and Li is the axial length of the i-th partition.

6. The radial forging and rolling process for the guide wheel rim according to claim 1, characterized in that, It also includes abnormal operating condition handling steps: when the temperature difference between the thick and thin areas is less than 80℃, extend the dwell time in the heat preservation channel or start the local induction heating device; when the temperature difference is greater than 200℃, start the forced air cooling of the thin area and speed up the transfer speed; when the radial force of the main roller exceeds 120% of the preset value or the axial widening rate exceeds 0.5mm / s, reduce the feed speed to 0.1mm / s and increase the pressure of the axial limit roller; if the radial force continues to rise, stop the feed and keep it idling.

7. The radial forging and rolling process for the guide wheel rim according to claim 1, characterized in that, In step S3, the temperature difference field is formed by controlling the forced air cooling of the thin area and supplementing the heating of the thick area with a local induction heating device.

8. The radial forging and rolling process for the guide wheel rim according to claim 1, characterized in that, In step S2, the wall thickness of the preform is measured in real time using a laser profile scanner, and the pressing amount of each partition hammer is dynamically corrected by the partition pressing control unit to keep the wall thickness deviation within ±0.5mm.

9. The radial forging and rolling process for the guide wheel rim according to claim 1, characterized in that, In step S4, the axial widening rate and the radial force of the main roll are monitored in real time using a radial force sensor and a laser profile scanner, and the feed speed is dynamically adjusted by a feed servo system. When the axial widening rate exceeds 0.4 mm / s, the feed speed is automatically reduced and the pressure of the axial limit roll is increased.

10. The radial forging and rolling process for the guide wheel rim according to any one of claims 1 to 9, characterized in that, The medium carbon microalloyed steel is 42CrMo steel or 40Mn2V steel; the process also includes step S6, post-processing: isothermal normalizing or quenching and tempering of the wheel rim after ring rolling, with a finishing allowance of 1-2 mm on each side.

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