Transmission shaft heat treatment temperature control method and heat treatment process
By calculating the thermal hysteresis coefficient Ki and temperature difference inversion, combined with adaptive heat preservation control, the temperature difference problem caused by diameter differences in the heat treatment of the drive shaft was solved, achieving precise temperature control and improving the quality and reliability of the drive shaft.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG SHENFA HEAVY IND MASCH TECH CO LTD
- Filing Date
- 2026-03-30
- Publication Date
- 2026-06-05
AI Technical Summary
In the existing heat treatment process for drive shafts, the significant difference in thermal inertia caused by the difference in diameter of the stepped sections is not fully considered. This results in excessive internal and external temperature differences, insufficient core heating, or surface overheating, which affects the hardness, toughness, and fatigue strength of the drive shaft and poses a risk of deformation and cracking.
By calculating the thermal hysteresis coefficient Ki, real-time temperature is collected and internal temperature is inverted. Temperature difference threshold and adaptive heat preservation control are set, and the heating rate is adjusted in segments to ensure that the internal and external temperature difference is within the allowable range. The heat dissipation conduction algorithm and temperature difference constraint judgment are used to achieve segmented differentiated temperature control.
It improves temperature control accuracy, significantly reduces the risk of drive shaft deformation and cracking, increases product qualification rate, and ensures uniform mechanical properties and service life of each stage.
Smart Images
Figure CN122147032A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of heat treatment technology, and more specifically, to a method and process for temperature control during heat treatment of a drive shaft. Background Technology
[0002] As a core load-bearing component of mechanical transmission systems, drive shafts are widely used in high-end equipment fields such as shipbuilding, construction machinery, automobiles, and wind power. Among them, multi-stage drive shafts have become the mainstream structural form in industrial production because they can adapt to the assembly requirements of different components. For large-sized drive shafts, precise temperature control is required during heat treatment to achieve simultaneous heat penetration and uniform cooling of the surface and core. This ensures that their mechanical properties, such as hardness, toughness, and wear resistance, meet the standards. At the same time, strict control must be exercised over deformation and cracking risks to avoid equipment malfunctions or even safety accidents caused by heat treatment defects. Existing methods for controlling the temperature of drive shaft heat treatment often employ a crude control approach of "uniform heating of the entire shaft at a fixed heating rate." This approach fails to adequately consider the core issue of significantly different thermal inertia caused by variations in the diameter of the stepped sections. The thicker sections have larger diameters and greater thermal inertia, resulting in a noticeable lag in the heating of the core. This can easily lead to excessive internal and external temperature differences and insufficient core heating, resulting in uneven microstructure and substandard hardness. Conversely, the thinner sections have smaller diameters and lower thermal inertia, leading to excessively rapid surface heating. This can easily cause overheating and coarse grains, thereby reducing the fatigue strength and service life of the drive shaft. In severe cases, it can even lead to premature failure of the drive shaft. Therefore, these methods have shortcomings. Summary of the Invention
[0003] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method and process for controlling the temperature of a transmission shaft during heat treatment, thereby reducing the temperature difference between the inner and outer shafts and improving product quality.
[0004] To achieve the above objectives, the present invention adopts the following technical solution: a method for temperature control during heat treatment of a drive shaft, comprising the following steps: S1: calculating and obtaining the thermal hysteresis coefficient K for each step of the drive shaft. i S2: Real-time acquisition of drive shaft temperature and internal temperature inversion: Obtain the surface temperature T_si(t) of each step of the drive shaft, based on the thermal hysteresis coefficient K of each step. i The real-time core temperature T_ci(t) of each step is obtained by using a heat dissipation and conduction algorithm, and then the real-time internal and external temperature difference ΔT of each step is calculated. i(t)=T_si(t)-T_ci(t), where k is the sampling time; S3, temperature difference constraint judgment: set the internal and external temperature difference threshold as ΔT_allow, obtain the maximum internal and external temperature difference value ΔT_max of each step of the drive shaft. If ΔT_max≤ΔT_allow, proceed to step S4. If ΔT_max>ΔT_allow, stop heating and enter the heat preservation stage until ΔT_max≤ΔT_allow, then proceed to step S4; S4: calculate the heating rate v of each step of the drive shaft. i and at the obtained heating rate v i The minimum value in the value is used as the actual heating rate to control the heat treatment furnace body to heat up at the actual heating rate.
[0005] Furthermore, the thermal hysteresis coefficient K i =λ / (cρ×Di 2 ), where λ is the thermal conductivity, c is the specific heat capacity, and D i Let be the diameter of each step of the drive shaft, and i be the segment number of each step of the drive shaft.
[0006] Furthermore, the inversion formula in step S2 is: T_ci(k+1) = T_ci(k) + K i ×(T_si(k)-T_ci(k))×Δt, where Δt is the sampling period.
[0007] Furthermore, the heating rate v i =v_base×(D_ref / D i )^1.5×(ΔT_allow / ΔT i ), where v_base is the base heating rate and D_ref is the reference diameter.
[0008] Furthermore, the reference heating rate v_base ranges from 5℃ / min to 20℃ / min, and the reference diameter D_ref is the arithmetic mean of each step of the drive shaft.
[0009] Furthermore, in step S3, when ΔT_max > ΔT_allow, the heat preservation time after entering the heat preservation stage is t_soak = t_base + K_t × ΔT_max, where t_base is the base heat preservation time and K_t is the heat preservation compensation coefficient.
[0010] Furthermore, the thermal insulation compensation coefficient K_t ranges from 0.1h / ℃ to 0.3h / ℃.
[0011] Furthermore, when the maximum internal and external temperature difference ΔT_max exceeds the internal and external temperature difference threshold ΔT_allow by more than 10℃, the insulation compensation coefficient K_t takes the upper limit value.
[0012] Furthermore, the internal and external temperature difference threshold ΔT_allow ranges from 30℃ to 50℃.
[0013] A heat treatment process for a drive shaft, which uses a temperature control method for heat treatment of the drive shaft to raise the temperature.
[0014] In summary, the present invention has the following beneficial effects:
[0015] 1. This invention calculates the thermal hysteresis coefficient K in segments. i It fully considers the thermal inertia differences caused by different diameters of the stepped drive shaft, providing a precise basis for subsequent core temperature inversion and heating rate control. It completely solves the drawback of traditional whole-shaft uniform temperature control ignoring diameter differences, realizes "segmented differentiated temperature control", ensures that each stepped segment can be in the optimal heating state, and effectively improves temperature control accuracy.
[0016] 2. By using temperature difference constraint judgment and adaptive heat preservation control, when the internal and external temperature difference exceeds the standard, the heating will be automatically stopped and the heat preservation time will be adjusted according to the size of the temperature difference. This ensures that the internal and external temperature difference of all steps is controlled within the allowable range, thereby reducing thermal stress from the source, controlling the deformation of the drive shaft to within 0.05mm, reducing the cracking defect rate by more than 80%, and significantly improving the product qualification rate. Attached Figure Description
[0017] Figure 1 Flowchart for an embodiment;
[0018] Figure 2 This is a schematic diagram showing the distribution of the drive shaft in the heat treatment furnace. Detailed Implementation
[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] like Figure 1 , Figure 2 As shown in the figure, this embodiment discloses a method for temperature control during heat treatment of a drive shaft, including the following steps:
[0021] S1: Calculate the thermal hysteresis coefficient K for each step of the drive shaft. i ;
[0022] Specifically, such as Figure 2As shown, the drive shaft has a multi-step structure, with each step having a different diameter. This drive shaft is mainly used in marine gearboxes. The diameter of the thinner section of the drive shaft is around 100mm, while the diameter of the thicker section exceeds 200mm, classifying it as a relatively large drive shaft. This results in differences in its internal and external thermal inertia and thermal conductivity. The thermal hysteresis coefficient Ki is used to characterize the degree of temperature hysteresis difference between the outer surface and the inner core of each step. Its calculation formula is: K i =λ / (cρ×D i 2 ), where λ is the thermal conductivity of the drive shaft material, c is the specific heat capacity of the drive shaft material, ρ is the density of the drive shaft material, and D i Let be the diameter of each stepped segment of the drive shaft, and ...
[0023] The λ, c, and ρ parameters of drive shafts vary depending on their material. These parameters can be determined by consulting relevant material handbooks based on the specific material being used (e.g., high-strength alloy steels such as 42CrMo and 34CrNiMo6). The diameter D of each step segment... i The thermal hysteresis coefficient K can be obtained by measuring the geometric dimensions of the drive shaft, based on the specifications on the process drawings. Individual measurements are not required. i The calculations are accurate, providing a reliable foundation for subsequent core temperature inversion and heating rate calculations.
[0024] S2: Real-time acquisition of drive shaft temperature and internal temperature inversion: Obtain the surface temperature T_si(t) of each step of the drive shaft, based on the thermal hysteresis coefficient K of each step. i The real-time core temperature T_ci(t) of each step is obtained by using a heat dissipation and conduction algorithm, and then the real-time internal and external temperature difference ΔT of each step is calculated. i (t)=T_si(t)-T_ci(t), where k is the sampling time;
[0025] In this step, the surface temperature T_si(t) is acquired in real time using an infrared thermometer installed inside the heat treatment furnace. At least one temperature measurement point is set for each step to ensure accurate capture of surface temperature changes in each step. The sampling time k is the time node for temperature acquisition.
[0026] Since the core temperature T_ci(t) cannot be directly measured, an inversion algorithm based on heat dissipation and conduction is used. The inversion formula is: T_ci(k+1) = T_ci(k) + K i ×(T_si(k)-T_ci(k))×Δt, where Δt is the sampling period, i.e., the time interval between two adjacent sampling times k and k+1. This inversion formula is derived based on the principle of heat conduction. By using the difference between the surface temperature and the core temperature, combined with the thermal hysteresis coefficient and the sampling period, the core temperature is calculated in real time, and then the internal and external temperature difference ΔT of each step segment is calculated. i (t) enables the monitoring of the temperature difference between the inside and outside.
[0027] Using this inversion method, the error of the core temperature inversion is controlled within ±2℃. Compared with the traditional empirical estimation (error of more than ±8℃), the accuracy is significantly improved. It can accurately capture the internal and external temperature difference changes in each step, providing reliable data support for subsequent temperature difference constraints and effectively avoiding temperature control failure caused by temperature difference estimation deviation.
[0028] S3: Temperature difference constraint judgment: Set the internal and external temperature difference threshold to ΔT_allow, obtain the maximum internal and external temperature difference value ΔT_max of each step of the drive shaft. If ΔT_max≤ΔT_allow, proceed to step S4. If ΔT_max>ΔT_allow, stop heating and enter the heat preservation stage until ΔT_max≤ΔT_allow before proceeding to step S4.
[0029] The internal and external temperature difference threshold ΔT_allow ranges from 30℃ to 50℃. Specifically, ΔT_allow is set based on the material, diameter, and heat treatment requirements of the drive shaft to limit the maximum permissible internal and external temperature difference, preventing excessive temperature differences from causing thermal stress that could lead to drive shaft deformation or cracking. ΔT_max represents the internal and external temperature difference ΔT for all stepped segments. i The maximum value in (t) directly reflects the temperature difference control of the entire drive shaft. If ΔT_max≤ΔT_allow, it means that the internal and external temperature differences of all stepped sections are within the allowable range, and the temperature can continue to rise. If ΔT_max>ΔT_allow, it means that the internal and external temperature differences of some stepped sections exceed the standard, and the temperature rise needs to be stopped and the heat preservation stage needs to be entered. Through heat preservation, the core temperature can gradually catch up with the surface temperature, and the internal and external temperature differences can be reduced.
[0030] Furthermore, the heat preservation time after entering the heat preservation stage is t_soak = t_base + K_t × ΔT_max, where t_base is the baseline heat preservation time and K_t is the heat preservation compensation coefficient. The baseline heat preservation time t_base is set according to the material and overall size of the drive shaft and is the basic heat preservation duration; the heat preservation compensation coefficient K_t is used to adaptively adjust the heat preservation time according to the temperature difference. The larger the temperature difference, the longer the heat preservation time, to ensure that the internal and external temperature difference can be reduced sufficiently. The value range of K_t is 0.1h / ℃ to 0.3h / ℃.
[0031] When ΔT_max exceeds ΔT_allow by more than 10℃, K_t takes the upper limit (0.3h / ℃) to accelerate temperature difference convergence, avoid thermal stress accumulation due to excessive temperature difference, and further reduce the risk of drive shaft deformation and cracking. During the heat preservation process, the internal and external temperature difference of each step is continuously monitored. When ΔT_max ≤ ΔT_allow, the heat preservation ends and proceeds to step S4.
[0032] As a further setting, during the heat preservation process, when ΔT_max just drops to ΔT_allow, the heat preservation is not immediately ended. Instead, it is waited until ΔT_max ≤ ΔT_allow - 10℃ before ending the heat preservation and proceeding to step S4, so that the temperature difference between the inside and outside is within a smaller range.
[0033] S4: Calculate the heating rate v of each step of the drive shaft. i and at the obtained heating rate v i The minimum value in the value is used as the actual heating rate to control the heat treatment furnace body to heat up at the actual heating rate.
[0034] The heating rate v of each step i Based on its diameter and the current internal and external temperature difference, an adaptive calculation is performed. The calculation formula is: v i =v_base×(D_ref / D i )^1.5×(ΔT_allow / ΔT i ), where v_base is the base heating rate and D_ref is the reference diameter.
[0035] The reference heating rate v_base ranges from 5℃ / min to 20℃, and can be determined based on the maximum diameter of the drive shaft and the thermal conductivity of the material. The larger the diameter and the lower the thermal conductivity, the smaller the value of v_base should be to avoid excessively rapid heating of the thicker sections, which could lead to a widening of the internal and external temperature difference. The reference diameter D_ref is the arithmetic mean of the various steps of the drive shaft, i.e., D_ref = (D1 + D2 + ... + D...). n ) / n (where n is the number of steps), ensuring a unified calculation basis for the heating rate and achieving a reasonable match of heating rates for different steps.
[0036] In the calculation formula, (D_ref / D i )^1.5 is the diameter compensation factor, D i The larger (bold paragraph), the smaller the factor, v i The smaller the value, the less likely the coarse section will heat up too quickly; (ΔT_allow / ΔT) i ) is the temperature difference compensation factor, ΔT i The larger the value, the smaller the factor, v i The smaller the value, the more effective the closed-loop correction for the internal and external temperature differences. The heating rate v for all temperature steps is calculated. i Then, the minimum value is selected as the actual heating rate to control the furnace body temperature rise, ensuring that all stepped sections are within the safe heating range, avoiding excessive temperature difference in the coarse section and preventing overheating in the fine section, thus achieving uniform heating of the entire drive shaft.
[0037] A heat treatment process for a drive shaft, wherein the temperature is raised using the aforementioned heat treatment temperature control method for drive shafts.
[0038] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.
Claims
1. A method for temperature control during heat treatment of a drive shaft, characterized in that, Includes the following steps: S1: Calculate the thermal hysteresis coefficient K for each step of the drive shaft. i ; S2: Real-time acquisition of drive shaft temperature and internal temperature inversion: Obtain the surface temperature T_si(t) of each step of the drive shaft, based on the thermal hysteresis coefficient K of each step. i The real-time core temperature T_ci(t) of each step is obtained by using a heat dissipation and conduction algorithm, and then the real-time internal and external temperature difference ΔT of each step is calculated. i (t)=T_si(t)-T_ci(t), where k is the sampling time; S3, Temperature difference constraint judgment: Set the internal and external temperature difference threshold to ΔT_allow, obtain the maximum internal and external temperature difference value ΔT_max of each step of the drive shaft. If ΔT_max≤ΔT_allow, proceed to step S4. If ΔT_max>ΔT_allow, stop heating and enter the heat preservation stage until ΔT_max≤ΔT_allow before proceeding to step S4. S4: Calculate the heating rate v of each step of the drive shaft. i and at the obtained heating rate v i The minimum value in the value is used as the actual heating rate to control the heat treatment furnace body to heat up at the actual heating rate.
2. The method for temperature control during heat treatment of a transmission shaft according to claim 1, characterized in that, Thermal hysteresis coefficient K i =λ / (cρ×D i 2 ), where λ is the thermal conductivity, c is the specific heat capacity, and D i Let be the diameter of each step of the drive shaft, and i be the segment number of each step of the drive shaft.
3. The method for temperature control during heat treatment of a transmission shaft according to claim 1, characterized in that, The inversion formula in step S2 is: T_ci(k+1) = T_ci(k) + K i ×(T_si(k)-T_ci(k))×Δt, where Δt is the sampling period.
4. The method for temperature control during heat treatment of a transmission shaft according to claim 1, characterized in that, heating rate v i =v_base×(D_ref / D i )^1.5×(ΔT_allow / ΔT i ), where v_base is the base heating rate and D_ref is the reference diameter.
5. The method for temperature control during heat treatment of a transmission shaft according to claim 4, characterized in that, The reference heating rate v_base ranges from 5℃ / min to 20℃ / min, and the reference diameter D_ref is the arithmetic mean of each step of the drive shaft.
6. The method for temperature control during heat treatment of a transmission shaft according to claim 1, characterized in that, In step S3, when ΔT_max > ΔT_allow, the heat preservation time after entering the heat preservation stage is t_soak = t_base + K_t × ΔT_max, where t_base is the baseline heat preservation time and K_t is the heat preservation compensation coefficient.
7. The method for temperature control during heat treatment of a transmission shaft according to claim 6, characterized in that, The thermal insulation compensation coefficient K_t ranges from 0.1h / ℃ to 0.3h / ℃.
8. The method for temperature control during heat treatment of a transmission shaft according to claim 7, characterized in that, When the maximum internal and external temperature difference ΔT_max exceeds the internal and external temperature difference threshold ΔT_allow by more than 10℃, the thermal insulation compensation coefficient K_t takes the upper limit value.
9. The method for temperature control during heat treatment of a transmission shaft according to claim 1, characterized in that, The internal and external temperature difference threshold ΔT_allow ranges from 30℃ to 50℃.
10. A heat treatment process for a drive shaft, characterized in that, The temperature is increased using the temperature control method described in any one of claims 1-9.