Manufacturing method of one-piece track shoe for special vehicle

Abstract

The invention discloses a manufacturing method of a one-piece track shoe for a special vehicle. The manufacturing method comprises the following steps that the weight of a forging stock is calculated, and blanking is conducted; horizontally placing the blanked round steel into a furnace in a single-layer manner, carrying out heat preservation, starting forging, and trimming by utilizing waste heat after forging is completed; the track shoe is flatly loaded into a material frame to be subjected to heat treatment, and shot blasting treatment is conducted on the track shoe after heat treatment is completed; a boring machine clamp is designed and manufactured, the boring machine clamp is installed on a common boring machine or a horizontal machining center, and the sizes of the two end faces, the pin holes, the end faces of the U-shaped grooves, the chamfers and the landing ribs of the track shoe are machined to the final sizes at a time; the landing rib is subjected to medium-frequency quenching treatment; and carrying out low-temperature tempering treatment on the whole track shoe after medium-frequency quenching. The method has the characteristics of high processing quality and efficiency, low production cost and the like, and is worthy of popularization and application.

Description

Technical Field

[0001] The invention relates to a method for manufacturing a one-piece track shoe for a special vehicle. Background Art

[0002] Track shoes are key parts of the walking system of special vehicles. They are in direct contact with the road surface during operation, bearing the weight of the entire vehicle, traction and friction with the road surface. Due to complex stresses such as impact, stretching, extrusion and bending, they are easily damaged by excessive wear and deformation during use, leading to failure. Therefore, the substrate of the track shoe is required to have good toughness and the ground reinforcement has high wear resistance.

[0003] There are two common ways to make track shoes for special vehicles: casting and forging. The material of cast track shoes is mainly high manganese steel, and the material of forged track shoes is mainly medium carbon alloy steel. As special vehicles develop towards lightweight, high mobility and high reliability and need to adapt to the requirements of complex and harsh working conditions, traditional cast track shoes are difficult to meet their performance requirements. Medium carbon alloy steel is now mostly used for forging. From a structural point of view, track shoes can be divided into single-body and one-piece types. The advantage of single-body track shoes is the simple manufacturing process, and the disadvantage is that the track is easy to fall off when the vehicle is maneuvering at high speed on complex and harsh working conditions. The one-piece track shoe solves the problem of the track falling off when the vehicle is maneuvering at high speed on complex and harsh working conditions, but its manufacturing process is relatively complicated. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for manufacturing a one-piece track shoe for special vehicles which has the advantages of simple operation, high processing quality and efficiency, and low production cost.

[0005] The technical solution of the present invention to solve the above technical problem is: a method for manufacturing a one-piece track shoe for a special vehicle, comprising the following steps:

[0006] Step 1: Calculate the weight of the forging billet and cut 42CrMoNbA round steel;

[0007] Step 2: Design and manufacture the forging die and trimming die of the track plate, and install the forging die and trimming die on a 2,500-ton electric screw press and a 315-ton closed single-point press respectively; heat the natural gas furnace, and then place the round steel that has been unloaded in a single layer flat in the furnace, and start forging after insulation. Feed and remove materials in a left-right-left-right cycle, and complete the forging of the track plate blank on the 2,500-ton electric screw press. After forging is completed, the blank is immediately transferred to the 315-ton closed single-point press to complete the trimming using the residual heat;

[0008] Step 3: Load the track plate flatly into the material frame, place the layers vertically at 90° and cross each other for heat treatment. After the heat treatment, the track plate is shot blasted to clean the oxide scale generated during forging and heat treatment.

[0009] Step 4: Design and manufacture the boring machine fixture, install the boring machine fixture on a common boring machine or horizontal machining center, and process the two end faces of the track shoe, pin holes, U-shaped groove end faces, chamfers, and ground rib dimensions to the final dimensions at one time;

[0010] Step 5: Perform medium frequency quenching on the grounding bar;

[0011] Step 6: After medium frequency quenching, the track plate is subjected to low temperature tempering as a whole.

[0012] In the method for manufacturing the one-piece track shoe for special vehicles, in the step 1, the mass fraction of Nb added in the 42CrMoNbA round steel is 0.02-0.05%, and Nb and C form NbC second phase particles, which have an inhibitory effect on the migration of steel grain boundaries within 1238°C, so that the track shoe obtains a fine-grained structure after forging and heat treatment, and the grains are 2 grades finer than those of the 42CrMoA steel track shoe manufactured by the same process.

[0013] The manufacturing method of the one-piece track shoe for special vehicles also includes a process of calculating the die forging deformation force before step 2: calculating the die forging deformation force P, P = W × Kw × F, W is the temperature and material coefficient, Kw is the pressure per unit area, F is the projected area of ​​the forging including the flash bridge part, and the die forging deformation force P≈39000KN is obtained.

[0014] In the method for manufacturing the one-piece track shoe for special vehicles, in step 2, the forging die and trimming die are made of 5CrNiMo steel, which is heat treated as a whole to 41-47HRC, and the working surface is ion nitrided at a temperature of 500°C.

[0015] In the method for manufacturing the one-piece track shoe for the above-mentioned special vehicle, in the step 2, the natural gas furnace is heated to 1180°C, the spacing of the round steels when loading the furnace is d / 2, d is the diameter of the round steels, forging begins after keeping warm for 40 to 50 minutes, 20 pieces are fed at a time, and the surface temperature of the forging is not lower than 850°C during trimming; forging begins after keeping warm at 1180°C, the temperature and material coefficient changes from 1.1 to 1.0, the required deformation force decreases from 43,000 KN to 39,000 KN, and the forging blank of the track shoe can be formed in one fire using only a 2,500-ton electric screw press.

[0016] In the method for manufacturing the one-piece track shoe for the above-mentioned special vehicle, in the step three, the heating equipment is a box-type or pit-type resistance furnace, the quenching parameters are: the quenching temperature is 850±10°C, the quenching time is 120-150min, the quenching method is oil cooling, and the tempering parameters are: the tempering temperature is 520±20°C, the tempering time is 180-210min, and the tempering method is water cooling.

[0017] In the method for manufacturing the one-piece track shoe for the above-mentioned special vehicle, in step four, the boring machine fixture includes a clamping body and a positioning plate, the clamping body positions the outer walls of the two holes of the track shoe through a V-shaped positioning surface, and the clamping body and the positioning plate realize the 90° and 180° transformation of the track shoe clamping posture through horizontal rotation and indexing.

[0018] In the manufacturing method of the one-piece track shoe for special vehicles, in the fourth step, the two end surfaces of the track shoe are first bored and milled; then the pin holes are drilled: a Φ34.5 mm pre-hole is first drilled on one side, and the pre-hole is processed to The boring machine fixture rotates 180° to bore and mill the other end face, drill a Φ34.5mm pre-hole on the other side, and use a boring tool to machine the pre-hole to The pin hole is drilled; then the boring machine fixture is rotated 90 degrees to mill the U-groove end face, chamfer, and ground rib, and then processed to the final size.

[0019] In the method for manufacturing the one-piece track shoe for the above-mentioned special vehicle, in the step five, the quenching medium is a 6% PAG aqueous solution, and a double-rib segmented heating scanning quenching method is adopted, and the 8 ground ribs are heated and spray-cooled 4 times, and the distance between the 8 ground ribs and the sensor is consistent; the quenching temperature is 850-880°C, and the color of the ground ribs after induction heating is orange-yellow and slightly reddish.

[0020] In the method for manufacturing the one-piece track shoe for special vehicles, in step six, the tempering temperature is 150° C. and the insulation time is 120 to 180 minutes.

[0021] The beneficial effects of the present invention are:

[0022] 1. The common initial forging temperature of 42CrMoA steel is about 1150℃. Under normal conditions, a 4000-ton electric screw press is required for the one-fire die forging of the track plate blank. On this basis, increasing the initial forging temperature by more than 20℃ will cause abnormal growth of the material grains. The present invention reduces the tendency of excessive grain growth of the material by adding Nb elements, and can increase the initial forging temperature to 1180℃. The temperature and material coefficient changes from 1.1 to 1.0, and the required deformation force decreases from 43000KN to 39000KN. Only a 2500-ton electric screw press (long-term operating allowable load of 40000KN) is needed to forge the track plate blank in one fire.

[0023] 2. The present invention adopts a 2500-ton electric screw press for one-fire forging, which can reduce the energy consumption generated by forging, broaden the application range of the equipment, and improve the utilization rate of the equipment, which is beneficial to small-batch production or short-term production and manufacturing.

[0024] 3. The present invention adds 0.02-0.05% Nb (niobium) by mass to 42CrMoA steel. After all hot working is completed, the grain size of the track shoe substrate (non-intermediate frequency quenching part) can be greater than level 8, which is more than 2 levels finer than 42CrMoA steel without Nb.

[0025] 4. The tempering temperature of 5CrNiMo steel forging die and trimming die is 510℃, and the ion nitriding temperature is 500℃. While maintaining the overall performance of the forging die and trimming die, the hardness, wear resistance and service life of the working surface are improved.

[0026] 5. The present invention loads the track plates into the material frame flatly, and the layers are vertically and cross-placed at 90 degrees. The track plates are cross-placed at 90 degrees to obtain a good hardening effect and small deformation during heat treatment.

[0027] 6. The pin hole is processed to the upper deviation in the machining process, and the pin hole diameter shrinks by ≤0.05mm in the induction heat treatment process. After the pin hole diameter shrinks, its size still meets the technical requirements Secondary processing is avoided and production efficiency is improved.

[0028] 7. The boring machine fixture includes a clamping body and a positioning plate. The clamping body and the positioning plate can realize the 90° and 180° change of the track shoe clamping posture through horizontal rotation and indexing. The boring machine fixture can realize the accurate rotation of parts and improve the boring efficiency by ≥20% while ensuring the coaxiality of the track shoe pin hole ≤0.1mm.

[0029] 8. When forging, the ground ribs are prepared with a reserve and then machined flat. During medium-frequency induction heating, the eight ground ribs are kept at the same distance from the sensor, ensuring that the final hardened layer depth is between 8 and 10 mm and the heat-affected zone is small, which will not affect the hardness of the track shoe substrate. This ensures that the ground ribs have high wear resistance while other parts still have good toughness.

[0030] 9. Under the premise of ensuring quality, the manufacturing cost of a single piece of the present invention can be reduced by about 7% (calculated based on a single-piece base value of 120 yuan, the material cost increases by 1.5 yuan / piece after adding Nb. Compared with a 4000-ton electric screw press, the manufacturing cost of a 2500-ton electric screw press can be reduced by 10 yuan / piece). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a flow chart of the present invention.

[0032] Figure 2 It is a schematic diagram of the structure of a one-piece track shoe.

[0033] Figure 3 for Figure 2 Side view of.

[0034] Figure 4 This is a top view of the forging die.

[0035] Figure 5 This is a top view of the trimming die.

[0036] Figure 6 This is a real picture of the uncut forged track plate blank.

[0037] Figure 7 This is the actual picture of the track shoe after machining.

[0038] Figure 8 This is a schematic diagram of the boring machine fixture structure.

[0039] Fig. 9 for Figure 8 Side view of.

[0040] Fig.10 This is the grain morphology of the finished matrix of 42CrMoA steel track shoe when forged at 1180℃.

[0041] Fig.11 This is the grain morphology of the finished matrix of 42CrMoNbA steel track shoe when forged at 1180℃. DETAILED DESCRIPTION

[0042] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0043] like Figure 1 As shown, a method for manufacturing a one-piece track shoe for a special vehicle comprises the following steps:

[0044] Step 1: Calculate the weight of the forging blank and cut the 42CrMoNbA round steel with a size of Φ80×245mm. Use a saw blade grinder to cut the steel.

[0045] The mass fraction of Nb added in 42CrMoNbA round steel is 0.02-0.05%. Nb and C form NbC second phase particles, which hinder the migration of steel grain boundaries within 1238°C, so that the track plate obtains a fine-grained structure after forging and heat treatment, and the grains are two grades finer than those of 42CrMoA steel track plates made by the same process.

[0046] Step 2: Calculate the process of die forging deformation force: Calculate the die forging deformation force P, P = W × Kw × F, W is the temperature and material coefficient, Kw is the pressure per unit area, F is the projected area of ​​the forging including the flash bridge, and the die forging deformation force P ≈ 39000KN is obtained.

[0047] Design and manufacture forging dies and trimming dies for track shoes. Forging dies and trimming dies such as Figure 4 , Figure 5As shown, the forging die and the trimming die are installed on a 2500-ton electric screw press and a 315-ton closed single-point press respectively; the natural gas furnace is heated to 1180°C, and then the round steel that has been unloaded is placed flat in a single layer and loaded into the furnace. The spacing between the round steels when loading the furnace is d / 2, where d is the diameter of the round steel. After keeping warm for 40 to 50 minutes, forging begins, and 20 pieces are fed at a time. The feeding and taking out of the track plate blank are cyclically fed in a left-right-left-right pattern. The forging of the track plate blank is completed on the 2500-ton electric screw press. After forging is completed, the blank is immediately transferred to the 315-ton closed single-point press, and the trimming is completed using the residual heat. The surface temperature of the forging is not lower than 850°C during trimming. Figure 6 This is a real picture of the uncut forged track plate blank. Figure 7 This is the actual picture of the track shoe after machining.

[0048] The forging die and trimming die are made of 5CrNiMo steel, which are heat treated as a whole to 41-47HRC. The working surface is ion nitrided at a temperature of 500°C.

[0049] After keeping at 1180℃, forging begins. The temperature and material coefficient changes from 1.1 to 1.0, and the required deformation force drops from 43000KN to 39000KN. Only a 2500-ton electric screw press (long-term allowable load of 40000KN) is needed to form the track plate forging blank in one fire.

[0050] Step 3: Calculate the quenching temperature t. 42CrMoA is a hypoeutectoid steel, t = Ac3 + 30 ~ 70 ° C, A C3 =723-10.7Mn-16.9Ni+29Si+16.9Cr+290As+16.38W, where Ac3 is the complete austenitization temperature of hypoeutectoid steel, and Mn, Ni, Si, Cr, As, and W are the mass fractions of the corresponding elements in steel. It can be seen that the quenching temperature will not change after adding Nb, so the heat treatment parameters of 42CrMoA steel are still used for quenching + tempering.

[0051] Load the track plate flatly into the material frame, and place the layers vertically at 90°. The track plate can be placed crosswise at 90° to obtain good hardening effect and small deformation during heat treatment. For heat treatment, the heating equipment is a box-type or pit-type resistance furnace. The quenching parameters are: quenching temperature is 850±10℃, quenching time is 120~150min, quenching method is oil cooling, and tempering parameters are: tempering temperature is 520±20℃, tempering time is 180~210min, and tempering method is water cooling.

[0052] After heat treatment, the track plate is shot blasted to clean the oxide scale produced during forging and heat treatment.

[0053] Step 4: Design and manufacture the boring machine fixture, first bore and mill the two end surfaces of the track shoe; then drill the pin hole: first drill a Φ34.5mm pre-hole on one side, and use a boring tool to machine the pre-hole to The boring machine fixture rotates 180° to bore and mill the other end face, drill a Φ34.5mm pre-hole on the other side, and use a boring tool to machine the pre-hole to The pin hole is drilled; then the boring machine fixture is rotated 90 degrees to mill the U-groove end face, chamfer, and ground rib, and then processed to the final size.

[0054] like Figure 8 , Fig. 9 As shown, the boring machine fixture includes a clamp body 1 and a positioning plate 2. The clamp body 1 positions the outer walls of the two holes of the track shoe through a V-shaped positioning surface, and the clamp body 1 and the positioning plate 2 realize the 90° and 180° transformation of the track shoe clamping posture through horizontal rotation and indexing.

[0055] The milling, slotting, boring and other processes of the track shoe can be completed in one clamping with an ordinary boring machine or horizontal machining center, shortening the time for secondary clamping and alignment of the parts. At the same time, the fast indexing of the boring machine fixture can realize the accurate turning of the parts, shorten the length of the boring tool, reduce the vibration of the tool, and improve the processing efficiency of boring holes by ≥20% while ensuring the coaxiality of the track shoe pin hole ≤0.1mm.

[0056] The machining process will process the pin hole to the upper limit size. During the induction heat treatment, the pin hole diameter will shrink slightly, and its size after shrinkage still meets the technical requirements.

[0057] Step 5: Perform medium frequency quenching on the ground reinforcement.

[0058] The quenching medium is a 6% PAG aqueous solution. The double-rib segmented heating scanning quenching method is adopted. The 8 ground bars are heated and spray-cooled in 4 times. The distance between the 8 ground bars and the sensor is consistent, so that the depth of the hardened layer can be accurately controlled and the heat-affected zone is small, which will not affect the hardness of the track plate matrix. The ground bars have high wear resistance while other parts still have good strength and toughness; the quenching temperature is 850-880℃, and the color of the ground bars after induction heating is orange-yellow and slightly red.

[0059] Step 6: After medium frequency quenching, the track plate is subjected to low temperature tempering treatment as a whole. The tempering temperature is 150°C and the insulation time is 120 to 180 minutes.

[0060] like Fig.10 , Fig.11 As shown, the present invention adds 0.02-0.05% Nb (niobium) by mass to 42CrMoA steel. After all hot working is completed, the grain size of the track shoe substrate (non-intermediate frequency quenching part) can be greater than level 8, which is more than 2 levels finer than 42CrMoA steel without Nb.

Claims

1. A method for manufacturing a one-piece track shoe for a special vehicle, characterized in that: The following steps are involved: Step 1: Calculate the weight of the forging billet and cut 42CrMoNbA round steel; Step 2: Design and manufacture the forging die and trimming die of the track plate, and install the forging die and trimming die on a 2,500-ton electric screw press and a 315-ton closed single-point press respectively; heat the natural gas furnace, and then place the round steel that has been unloaded in a single layer flat in the furnace, and start forging after insulation. Feed and remove materials in a left-right-left-right cycle, and complete the forging of the track plate blank on the 2,500-ton electric screw press. After forging is completed, the blank is immediately transferred to the 315-ton closed single-point press to complete the trimming using the residual heat; Step 3: Load the track plate flatly into the material frame, place the layers vertically at 90° and cross each other for heat treatment. After the heat treatment, the track plate is shot blasted to clean the oxide scale generated during forging and heat treatment. Step 4: Design and manufacture the boring machine fixture, install the boring machine fixture on a common boring machine or horizontal machining center, and process the two end faces of the track shoe, pin holes, U-shaped groove end faces, chamfers, and ground rib dimensions to the final dimensions at one time; Step 5: Perform medium frequency quenching on the grounding bar; Step 6: After medium frequency quenching, the track plate is subjected to low temperature tempering as a whole.

2. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: In the step 1, the mass fraction of Nb added in the 42CrMoNbA round steel is 0.02-0.05%, and Nb and C form NbC second phase particles, which have an inhibitory effect on the migration of steel grain boundaries within 1238° C., so that the track plate obtains a fine-grained structure after forging and heat treatment, and the grains are 2 grades finer than those of the 42CrMoA steel track plate made by the same process.

3. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: Before step 2, the process of calculating the die forging deformation force is also included: calculating the die forging deformation force P, P = W × Kw × F, W is the temperature and material coefficient, Kw is the pressure per unit area, F is the projected area of ​​the forging including the flash bridge part, and the die forging deformation force P≈39000KN is obtained.

4. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: In the step 2, the forging die and trimming die are made of 5CrNiMo steel, which are heat treated as a whole to 41-47HRC, and the working surface is ion nitrided at a temperature of 500°C.

5. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: In the step 2, the natural gas furnace is heated to 1180°C, the spacing of the round steels when loading the furnace is d / 2, d is the diameter of the round steels, forging is started after keeping warm for 40 to 50 minutes, 20 pieces are fed at a time, and the surface temperature of the forging is not lower than 850°C during trimming; forging is started after keeping warm at 1180°C, the temperature and material coefficient changes from 1.1 to 1.0, the required deformation force decreases from 43000KN to 39000KN, and the forging blank of the crawler plate can be formed in one fire using only a 2500-ton electric screw press.

6. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: In the step three, the heating equipment is a box-type or pit-type resistance furnace, the quenching parameters are: the quenching temperature is 850±10°C, the quenching time is 120-150min, the quenching method is oil cooling, and the tempering parameters are: the tempering temperature is 520±20°C, the tempering time is 180-210min, and the tempering method is water cooling.

7. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: In step 4, the boring machine fixture includes a clamping body and a positioning plate. The clamping body positions the outer walls of the two holes of the track shoe through a V-shaped positioning surface. The clamping body and the positioning plate realize the 90° and 180° transformation of the track shoe clamping posture through horizontal rotation and indexing.

8. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: In the step 4, firstly, the two end surfaces of the track shoe are bored and milled; then, the pin holes are drilled: first, a Φ34.5 mm pre-hole is drilled on one side, and the pre-hole is processed to The boring machine fixture rotates 180° to bore and mill the other end face, drill a Φ34.5mm pre-hole on the other side, and use a boring tool to machine the pre-hole to The pin hole is drilled; then the boring machine fixture is rotated 90 degrees to mill the U-groove end face, chamfer, and ground rib, and then processed to the final size.

9. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: In the step five, the quenching medium is a 6% PAG aqueous solution, and a double-rib segmented heating scanning quenching method is adopted to heat the 8 ground bars in 4 times and spray cool them. The distance between the 8 ground bars and the sensor is consistent; the quenching temperature is 850-880°C, and the color of the ground bars after induction heating is orange-yellow and slightly reddish.

10. The method for manufacturing a one-piece track shoe for a special vehicle according to claim 1, characterized in that: In the step six, the tempering temperature is 150° C. and the holding time is 120 to 180 minutes.

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