Axle after-forging waste heat utilization heat treatment process

Abstract

The invention discloses a heat treatment process for utilizing waste heat after axle forging, which realizes efficient utilization of waste heat and accurate matching of process parameters through thermal state transfer, segmented temperature control cooling, temperature-time dynamic compensation and digital twin monitoring technologies. Compared with a traditional process, the production period is shortened by 58%, energy consumption is reduced by 40% or above, and the comprehensive performance of the axle is remarkably improved.

Description

Technical Field

[0001] The present invention relates to a heat treatment process for utilizing the waste heat after forging of an axle. Background Art

[0002] With the rapid development of the railway transportation industry, the railway transportation industry has put forward higher requirements for the performance of axles.

[0003] As a key component of railway vehicles, the main function of the axle is to transmit power and bear loads. In the production process, its mechanical properties and wear resistance are improved through heat treatment, and the heat treatment method of normalizing + tempering is usually adopted. Most of the axle production methods are to heat and forge the axle blank into shape, and after cooling to room temperature for 24 hours, heat treatment is carried out. When loading the furnace for heat treatment, it is necessary to slowly heat for 120 min - 160 min first, and then enter the insulation area for insulation. However, adopting this scheme not only prolongs the manufacturing cycle of the axle, but also greatly wastes the waste heat after forging of the axle, and reheating during heat treatment leads to a significant increase in production costs.

[0004] According to the technological characteristics of the train axle steel material and combined with the requirements of the axle performance, researching a production method that can make full use of the waste heat after forging of the axle, accelerate the heating rate of the axle heat treatment, reduce the power consumption of heating, and ensure that the axle performance meets the standard requirements has broad application prospects. Summary of the Invention

[0005] The purpose of the present invention is to provide a heat treatment process for utilizing the waste heat after forging of an axle to solve the problems raised in the above background art.

[0006] To achieve the above purpose, the present invention provides the following technical solution: A heat treatment process for utilizing the waste heat after forging of an axle, including the following steps:

[0007] (1) Hot state transfer: Transfer the forged axle directly to the heat treatment work area at a hot state of 800 - 950 °C through an automatic conveyor line;

[0008] (2) Controlled speed slow cooling: Actively control the temperature of the axle during transportation and slowly cool it to 400 - 500 °C at a rate of 5 - 15 °C / min;

[0009] (3) Intelligent clamping: Use a robotic arm equipped with an infrared temperature measurement function to monitor the temperature of the axle in real time. When the preset furnace loading temperature is reached, transfer the axle to the heat treatment equipment through a hydraulic clamping device;

[0010] (4) Dynamic matching: Adjust the heat treatment process parameters according to the real-time temperature of the axle, establish a temperature - holding time compensation model, and when the furnace loading temperature decreases by 50 °C each time, increase the holding time by 5 - 8%;

[0011] (5) Gradient heat treatment: Perform variable-temperature heat treatment on the hot-state furnace-loaded axle. In the initial stage, heat up to the normalizing temperature at a rate of 3-5 °C / min, and after the heat preservation ends, cool down to the tempering temperature at a rate of 10-15 °C / min.

[0012] Preferably, in step (2), segmented cooling control is adopted. When the temperature is above 600 °C, the cooling rate is controlled at 8-12 °C / min. When the temperature is in the range of 600-500 °C, the cooling rate is reduced to 5-8 °C / min, and natural air cooling is used below 500 °C.

[0013] Preferably, the hydraulic clamping device is provided with adaptive curved surface jaws, and a ceramic heat insulation layer is provided on the inner surface of the jaws. The clamping pressure is dynamically adjusted according to the axle diameter, and the adjustment range is 0.5-2.5 Mpa.

[0014] Preferably, the temperature-holding time compensation model satisfies the relationship t = t0×(1 + 0.05ΔT / 50), where t0 is the standard holding time, and ΔT is the difference between the actual furnace-loading temperature and the reference temperature of 500 °C.

[0015] Preferably, during the gradient heat treatment process, pulse heating is adopted in the normalizing stage. After heating for 5 minutes each time, heating is stopped for 1 minute for temperature equalization.

[0016] Preferably, an on-line detection station is set before step (3). The geometric dimensions of the axle are obtained in real time through a laser scanner, and the measurement data is fed back to the heat treatment equipment for automatic correction of process parameters.

[0017] Preferably, the automatic conveyor line is equipped with an electromagnetic induction temperature compensation device. When it is monitored that the axle temperature is lower than 400 °C, local temperature compensation is started to maintain the axle end temperature not lower than 350 °C.

[0018] Preferably, in the cooling stage of step (5), atomized cooling medium is used for gradient cooling, and the flow rate of the cooling medium is dynamically adjusted according to the wall thickness difference of different parts of the axle.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. The present invention adopts a process method of controlling the cooling rate and cooling temperature of the forged axle, and performs heat treatment on the hot-state axle in the furnace. When the axle is in the heating zone in the heat treatment furnace, the heating power of the heating zone is reduced, and the axle temperature reaches the holding temperature after two heating beats. The heating rate is effectively improved, and the energy consumption is reduced. 2. The present invention significantly improves the production efficiency, saves at least 24 hours of axle processing time, and the process implementation is simple, with a broad application scenario. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a flowchart of the waste heat hierarchical utilization of the present invention;

[0022] Figure 2 It is the temperature-holding time compensation curve; DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0024] See also Figure 1-2 The present invention provides a technical solution: a heat treatment process for utilizing residual heat after axle forging, comprising the following steps:

[0025] (1) Hot transfer: The forged axle is directly transferred to the heat treatment area at 800-950℃ through an automatic conveyor line;

[0026] (2) Speed-controlled slow cooling: Active temperature control is implemented on the axle during transportation, and it is slowly cooled to 400-500°C at a rate of 5-15°C / min;

[0027] (3) Intelligent clamping: A robotic arm equipped with infrared temperature measurement function monitors the axle temperature in real time. When the preset furnace loading temperature is reached, the axle is transferred to the heat treatment equipment through a hydraulic clamping device.

[0028] (4) Dynamic matching: Adjust the heat treatment process parameters according to the real-time temperature of the axle, establish a temperature-holding time compensation model, and increase the holding time by 5-8% for every 50°C decrease in the furnace temperature;

[0029] (5) Gradient heat treatment: The hot axle is subjected to variable temperature heat treatment. In the initial stage, the temperature is raised to the normalizing temperature at a rate of 3-5℃ / min, and after the insulation is completed, it is cooled to the tempering temperature at a rate of 10-15℃ / min.

[0030] In step (2), segmented cooling control is adopted. When the temperature is above 600°C, the cooling rate is controlled at 8 - 12°C / min. When the temperature is in the range of 600 - 500°C, the cooling rate is reduced to 5 - 8°C / min. Below 500°C, natural air cooling is used; the hydraulic clamping device is equipped with adaptive curved surface jaws, and a ceramic heat insulation layer is provided on the inner surface of the jaws. The clamping pressure is dynamically adjusted according to the axle diameter, and the adjustment range is 0.5 - 2.5 Mpa; the temperature-holding time compensation model satisfies the relationship t = t0×(1 + 0.05ΔT / 50), where t0 is the standard holding time and ΔT is the difference between the actual furnace loading temperature and the reference temperature of 500°C; during the gradient heat treatment process, pulse heating is used in the normalizing stage, and heating is stopped for 1 min every 5 min of heating for temperature equalization; before step (3), an on-line detection station is set up, and the geometric dimensions of the axle are obtained in real time through a laser scanner, and the measurement data is fed back to the heat treatment equipment for automatic correction of process parameters; the automatic conveyor line is equipped with an electromagnetic induction temperature compensation device, and when it is monitored that the axle temperature is lower than 400°C, local temperature compensation is started to maintain the axle end temperature not lower than 350°C; in the cooling stage of step (5), atomized cooling medium is used for gradient cooling, and the flow rate of the cooling medium is dynamically adjusted according to the wall thickness difference of different parts of the axle.

[0031] Process comparison:

[0032] Original heat treatment process Blanking → Heating → Forging → Furnace matching → Heat treatment (cold shaft) Current heat treatment process Furnace matching → Blanking → Heating → Forging → Heat treatment (hot shaft)

[0033] Performance comparison:

[0034]

[0035]

[0036] Energy saving comparison

[0037] Original heat treatment Current heat treatment Energy consumption savings Energy consumption 330 kw / root 309 kw / root 21 kw / root

[0038] Example 1:

[0039] LZ50 axle (diameter φ180mm)

[0040] Post-forging treatment: The temperature of the axle after forging is 920°C, and it is transferred through an electromagnetic conveyor line and forced air-cooled to 600°C

[0041] (Rate 10°C / min);

[0042] Temperature-controlled furnace loading: When the infrared temperature measurement shows that the axle temperature is 480°C, the manipulator grabs and loads it into the furnace (clamping pressure 1.8 MPa);

[0043] Dynamic heat treatment:

[0044] Normalizing: Pulse heating to 890°C, and the holding time is calculated as:

[0045] t = 90×(1 + 0.06×500 - 48050) = 92.16 min t = 90×(1 + 0.06×50500 - 48

[0046] 0) = 92.16 min

[0047] Tempering: Atomized cooling to 540 °C, flow rate adjusted according to the difference between the shaft body and journal (shaft body: 20 L / min,

[0048] journal: 15 L / min);

[0049] Quality inspection: Grain size 8, yield strength ≥ 345 MPa, fully meeting the Q / CR 1005 - 2023 standard.

[0050] Example 2:

[0051] Post - forging treatment:

[0052] After the axle is formed by die forging, the surface temperature is 935 °C, and it is transferred to the slow - cooling zone through an electromagnetic conveyor line, adopting a segmented temperature - control strategy:

[0053] The first stage (> 600 °C): Inject nitrogen to accelerate cooling, rate 12 °C / min

[0054] The second stage (500 - 600 °C): Auxiliary cooling with radiation plates, rate 7 °C / min

[0055] The third stage (< 500 °C): Natural air - cooling to the target temperature

[0056] Intelligent clamping process:

[0057] The infrared thermal imaging system monitors the temperature field distribution of the axle. When the axial temperature difference ≤ 15 °C and the average temperature reaches 470 °C, the six - degree - of - freedom robotic arm performs the grasping operation:

[0058] Clamping pressure P = 0.02D + 1.5 (MPa) / / D is the axle diameter (mm) => P = 0.02×220 + 1.5 = 5.9 MPa

[0059] Piezoelectric ceramic sensors are built into the jaws to provide real - time feedback of the contact stress, and the fluctuation range is controlled within ±0.3 MPa.

[0060] Dynamic heat treatment parameters

[0061] Normalizing stage:

[0062] Adopt a gradient heating strategy. In the initial stage, heat up to 900 °C at a rate of 3 °C / min, and then pulse heating (heating for 4 min / soaking for 1 min) to the target temperature of 910 °C

[0063] Calculation of soaking time:

[0064] t = 120×(1 + 0.06×(500 - 470) / 50) = 120×1.036 = 124.3 min

[0065] Tempering stage:

[0066] The ratio of the atomized cooling medium is adjusted to a water-based solution concentration of 15%, and the flow rate is controlled in zones:

[0067] Shaft body area: 25 L / min (wall thickness 65 mm)

[0068] Journal area: 18 L / min (wall thickness 45 mm)

[0069] Quality inspection results:

[0070] Test items Measured value CRRC standard requirements Surface hardness (HB) 285-302 269-311 Yield strength (MPa) 415 ≥390 Impact energy (J, -40°C) 52 ≥40 Grain size grade Grade 8.5 ≥ Grade 7

[0071] Effect of process optimization

[0072] Energy consumption comparison:

[0073] Traditional process: 3.8 kWh / kg

[0074] This embodiment: 2.1 kWh / kg (↓44.7%)

[0075] Production cycle:

[0076] Total time consumed: 980 min (original process 2350 min, shortened by 58.3%)

[0077] Deformation control:

[0078] Axial bending degree ≤ 0.15 mm / m, which is better than the deformation standard of 0.2 mm / m for high-speed train axles.

[0079] Although the embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A heat treatment process for utilizing residual heat after axle forging, characterized in that: The following steps are involved: (1) Hot transfer: The forged axle is directly transferred to the heat treatment area at 800-950℃ through an automatic conveyor line; (2) Speed-controlled slow cooling: Active temperature control is implemented on the axle during transportation, and it is slowly cooled to 400-500°C at a rate of 5-15°C / min; (3) Intelligent clamping: A robotic arm equipped with infrared temperature measurement function monitors the axle temperature in real time. When the preset furnace loading temperature is reached, the axle is transferred to the heat treatment equipment through a hydraulic clamping device. (4) Dynamic matching: Adjust the heat treatment process parameters according to the real-time temperature of the axle, establish a temperature-holding time compensation model, and increase the holding time by 5-8% for every 50°C decrease in the furnace temperature; (5) Gradient heat treatment: The hot axle is subjected to variable temperature heat treatment. In the initial stage, the temperature is raised to the normalizing temperature at a rate of 3-5℃ / min, and after the insulation is completed, it is cooled to the tempering temperature at a rate of 10-15℃ / min.

2. The heat treatment process for utilizing residual heat after axle forging according to claim 1 is characterized in that: In the step (2), segmented cooling control is adopted, and the cooling rate is controlled at 8-12°C / min above 600°C, the cooling rate is reduced to 5-8°C / min in the 600-500°C stage, and natural air cooling is adopted below 500°C.

3. The heat treatment process for utilizing residual heat after axle forging according to claim 1 is characterized in that: The hydraulic clamping device is provided with an adaptive curved surface clamping jaw, the inner surface of the clamping jaw is provided with a ceramic heat insulation layer, and the clamping pressure is dynamically adjusted according to the axle diameter, and the adjustment range is 0.5-2.5MPa.

4. The heat treatment process for utilizing residual heat after axle forging according to claim 1 is characterized in that: The temperature-holding time compensation model satisfies the relationship t=t0×(1+0.05ΔT / 50), wherein t0 is the standard holding time, and ΔT is the difference between the actual charging temperature and the reference temperature of 500°C.

5. The heat treatment process for utilizing residual heat after axle forging according to claim 1 is characterized in that: During the gradient heat treatment process, pulse heating is used in the normalizing stage, and heating is stopped for 1 minute after every 5 minutes of heating to balance the temperature.

6. The heat treatment process for utilizing residual heat after axle forging according to claim 1 is characterized in that: Before step (3), an online inspection station is set up to obtain the geometric dimensions of the axle in real time through a laser scanner, and the measurement data is fed back to the heat treatment equipment for automatic correction of process parameters.

7. The heat treatment process for utilizing residual heat after axle forging according to claim 1 is characterized in that: The automatic conveyor line is equipped with an electromagnetic induction temperature compensation device, which starts local temperature compensation when it detects that the axle temperature is lower than 400°C, maintaining the temperature of the axle end at no lower than 350°C.

8. The heat treatment process for utilizing residual heat after axle forging according to claim 1 is characterized in that: In the cooling stage of step (5), gradient cooling is performed using an atomized cooling medium, and the flow rate of the cooling medium is dynamically adjusted according to the difference in wall thickness of different parts of the axle.

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