Variable cross-section automobile plate spring short-process integrated production system and production method

Abstract

The invention relates to a short-process integrated production system and method for a variable-cross-section automobile plate spring, and belongs to the technical field of metallurgy. Comprising an integrated hot rolling unit; the integrated hot rolling unit comprises a spring flat steel hot rolling module, an on-line temperature control module and a variable cross-section rolling module which are sequentially connected along a production line. The spring flat steel hot rolling module comprises a heating furnace, a roughing mill group, an intermediate mill group, a finishing mill group and a reducing and sizing mill group which are connected in sequence, and is used for continuously rolling square billets; the on-line temperature control module is arranged on the rear side of the reducing and sizing unit and used for adjusting the rolling starting temperature of spring flat steel variable cross-section rolling. And the variable cross-section rolling module consists of a plurality of groups of hydraulic servo rollers with adjustable roller gaps and is used for continuously finishing variable cross-section rolling of the plate spring. The technological process of the variable cross-section plate spring can be shortened, the surface modification reheating procedure in a traditional technology is omitted, production energy consumption is reduced, the waste heat utilization rate is increased, and investment and operation cost is saved.

Description

Technical Field

[0001] The present invention belongs to the technical field of metallurgy, and relates to a short-process integrated production system and a production method for a variable-section automobile leaf spring. Background Art

[0002] Leaf springs are a crucial component of automotive suspension systems and a hot topic in lightweighting research. They weigh from tens to hundreds of kilograms, accounting for 8%-9% of a vehicle's weight. Optimizing their structure is crucial for reducing vehicle weight. Variable-section leaf springs are a key approach to lightweighting leaf springs, improving material utilization and reducing weight. These springs adjust their thickness along their length based on the load conditions, resulting in a thicker center and thinner ends. This optimization can reduce weight by over 30% while maintaining performance.

[0003] The main technical difficulty in producing variable-section leaf springs lies in the variable-section rolling process and the subsequent heat treatment and strengthening measures. In the leaf spring rolling production processes disclosed in patents CN 112171191B, CN 118880170 A, CN 111809034 B, and CN 118127418 A, the rolling, heat treatment, and surface modification processes are independent of each other, making it difficult to integrate resources between them and resulting in low space utilization. Furthermore, the rolled material requires repeated heating and cooling, resulting in low waste heat utilization and high energy costs. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a short-process integrated production system and production method for variable-section automobile leaf springs, which can realize integrated short-process production of rolling and heat treatment, and realize the "tempering + surface modification + strengthening" performance gradient optimization through the temperature zone division before variable-section rolling.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] A short-process integrated production system for variable-section automotive leaf springs, including an integrated hot-rolling mill;

[0007] The integrated hot rolling mill comprises a spring flat steel hot rolling module, an online temperature control module and a variable cross-section rolling module which are sequentially connected along the production line;

[0008] The spring flat steel hot rolling module includes a heating furnace, a roughing mill, an intermediate rolling mill, a finishing mill and a reducing and sizing mill connected in sequence, and is used for continuous rolling of square billets;

[0009] The online temperature control module is arranged at the rear side of the reducing and sizing unit and is used to adjust the starting rolling temperature of the spring flat steel variable cross-section rolling;

[0010] The variable-section rolling module is composed of multiple groups of hydraulic servo rollers with adjustable roll gaps, and is used to continuously complete the variable-section rolling of leaf springs.

[0011] Optionally, according to the short-process integrated production system for variable-section automobile leaf springs described in the present invention, the online temperature control module includes an electromagnetic heating device, a thermal insulation track, and an online cooling control device; online temperature calculation is performed based on the spring flat steel sizing rolling outlet temperature, the cross-sectional dimensions of the rolled piece, the operating speed, and the variable-section rolling start temperature requirements, and temperature control is performed through the electromagnetic heating device, the thermal insulation track, or the online cooling control device to adjust the starting rolling temperature of the spring flat steel variable-section rolling to a predetermined value.

[0012] Optionally, according to the short-process integrated production system for variable-section automobile leaf springs described in the present invention, the variable-section rolling module also includes an intelligent closed-loop control system, which includes a rolling force sensor and a temperature control sensor for real-time display of the roller pressure and roller temperature during variable-section rolling, and transmits the sensor signal to the controller. The controller adjusts the rolling parameters of multiple groups of hydraulic servo rollers in the variable-section rolling module to form closed-loop control.

[0013] Optionally, the short-process integrated production system for variable-section automobile leaf springs according to the present invention further includes a waste heat utilization module, which is integrated at the end of the variable-section rolling module and includes an insulation channel and a shot peening device, and utilizes the rolling waste heat to perform online tempering and surface strengthening treatment of the leaf spring.

[0014] Optionally, the short-process integrated production system for variable-section automobile leaf springs according to the present invention further includes a quality monitoring module, which is arranged at the end of the waste heat utilization module, and is based on real-time detection of the cross-sectional profile of the leaf spring, and feeds back the data to the variable-section rolling module for correction.

[0015] In addition, the present invention also provides a short-process integrated production method for variable-section automobile leaf springs, comprising the integrated production system described in the above embodiment and the following steps:

[0016] (1) Spring flat steel hot rolling stage: The steel is continuously rolled using rough rolling, intermediate rolling, finishing rolling and sizing mills. The rolling temperature is 800℃~1100℃ and the total deformation is 50%~95%;

[0017] (2) Online temperature control stage: Based on the outlet temperature of the spring flat steel sizing rolling, the cross-sectional dimensions of the rolled piece, the operating speed, and the starting temperature requirements of the variable cross-section rolling, online temperature calculation is performed, and different temperature control measures are taken to adjust the starting temperature of the spring flat steel variable cross-section rolling to the predetermined value;

[0018] (3) Variable cross-section rolling stage: adopt multi-pass asynchronous rolling process, the first pass rolling temperature is ≥950℃, the last pass rolling temperature is ≥650℃, and the total deformation is controlled at 50% to 85%;

[0019] (4) Residual heat treatment stage: by matching the rolling piece transmission speed, the leaf spring enters the residual heat utilization module within 10 seconds after rolling, and the tempering holding time is ≤60 seconds;

[0020] (5) Quality monitoring stage: Based on the real-time detection of the cross-sectional profile of the leaf spring, the data is fed back to the variable cross-section rolling stage for correction.

[0021] Optionally, according to the short-process integrated production method for variable-section automobile leaf springs of the present invention, during the hot rolling stage of the spring flat steel, the thickness of the spring flat steel ranges from 8 mm to 50 mm.

[0022] Optionally, according to the short-process integrated production method for variable-section automobile leaf springs of the present invention, in the variable-section rolling stage, the thickness range of the variable-section leaf spring is 0.5mm to 25mm, and the variable-section roller system in the variable-section rolling stage is continuously deformed ≥3 times.

[0023] Optionally, according to the short-process integrated production method for variable-section automobile leaf springs of the present invention, during the online temperature control stage:

[0024] The heating speed of the electromagnetic heating device is 5℃ / s~200℃ / s;

[0025] The online controlled cooling device uses online water cooling to reduce the temperature, and the cooling rate is 1℃ / s~50℃ / s;

[0026] The running speed of the insulation track is 0.1m / s~10m / s, and the slow cooling speed is 0.1℃ / s~5℃ / s.

[0027] Optionally, according to the short-process integrated production method for variable-section automobile leaf springs of the present invention, the residual heat treatment stage includes multiple temperature zones with successively decreasing temperatures, wherein the first temperature zone is used for tempering the leaf spring, the second temperature zone is simultaneously used for laser cladding wear-resistant layer deposition or plasma nitriding process, and the third temperature zone is used for high-pressure gas mist shot peening strengthening;

[0028] The temperature control range of the first temperature zone is 650°C to 550°C; the temperature control range of the second temperature zone is 550°C to 400°C; and the temperature control range of the third temperature zone is ≤400°C.

[0029] The beneficial effects of the present invention are:

[0030] 1) The rolling and heat treatment are integrated, with a short process, which is more than 30% shorter than the traditional process, saving investment and operating costs;

[0031] 2) Eliminating the need for reheating before conventional variable-section rolling and subsequent surface modification and reheating, the waste heat utilization module features multiple temperature zones. The first temperature zone (650°C to 550°C) performs tempering, the second temperature zone (550°C to 400°C) simultaneously performs laser cladding wear-resistant layer deposition or plasma nitriding, and the third temperature zone (≤400°C) performs high-pressure aerosol shot peening. This expands the traditional single waste heat tempering process into a three-stage combination of "tempering + surface modification + strengthening," achieving gradient optimization of material properties through temperature zone division.

[0032] 3) The waste heat utilization module is integrated at the end of the rolling line, using the waste heat from rolling to directly perform online tempering and surface strengthening treatment on the leaf spring. The waste heat utilization rate reaches over 85%, saving 40% to 50% energy compared to traditional processes that require additional heating furnaces.

[0033] 4) Continuous rolling and heat treatment can effectively avoid grain boundary oxidation and increase the fatigue life of leaf springs by ≥30%;

[0034] 5) Adapt to the production of multiple varieties and support the production of variable-section leaf springs with a thickness of 0.5-25mm and a length of 800mm to 2500mm.

[0035] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0037] Figure 1 This is a schematic diagram of the short-process integrated production process of the variable-section automobile leaf spring provided by the present invention;

[0038] Figure 2 This is a schematic diagram of a finished automobile leaf spring provided in one embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0040] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0041] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0042] See also Figure 1 and Figure 2 The figure shows a short-process integrated production system for variable-section automobile leaf springs, including an integrated hot rolling mill.

[0043] The integrated hot rolling mill includes a spring flat steel hot rolling module, an online temperature control module and a variable section rolling module which are sequentially connected along the production line.

[0044] The spring flat steel hot rolling module includes a heating furnace, a roughing mill, an intermediate rolling mill, a finishing mill and a reducing and sizing mill connected in sequence, and is used for continuous rolling of square billets.

[0045] The online temperature control module is set at the rear side of the sizing unit to adjust the starting rolling temperature of the spring flat steel variable cross-section rolling.

[0046] The variable-section rolling module consists of multiple sets of hydraulic servo rollers with adjustable roll gaps. The roll gap adjustment accuracy is ≤0.05mm and is used to continuously complete the variable-section rolling of leaf springs.

[0047] Furthermore, the online temperature control module includes independent electromagnetic heating devices, insulation rails and online cooling control devices; online temperature calculation is performed based on the outlet temperature of the spring flat steel sizing rolling, the cross-sectional dimensions of the rolled piece, the operating speed and the starting temperature requirements of the variable-section rolling, and temperature control is performed through the electromagnetic heating device or insulation rail or online cooling control device, such as electromagnetic induction heating, air cooling, insulation cover slow cooling and online water cooling, so as to adjust the starting temperature of the variable-section rolling of the spring flat steel to a predetermined value.

[0048] Furthermore, the variable-section rolling module also includes an intelligent closed-loop control system, including a rolling force sensor and a temperature control sensor, which are used to display the roll pressure and roll temperature during variable-section rolling in real time, and transmit the sensor signal to the controller. The controller adjusts the rolling parameters of multiple groups of hydraulic servo rolls in the variable-section rolling module to form a closed-loop control. According to the data fed back by the rolling force sensor, the parameters of the hydraulic servo rolls are adjusted in time to reduce the productivity of defective products. The present invention adopts non-contact infrared temperature measurement technology with a temperature measurement accuracy of ±5°C. Through an array layout (multiple temperature measurement units working synchronously), high-resolution, real-time monitoring of the surface or near-surface temperature field of the rolled piece is achieved. Its core advantages include:

[0049] Non-contact measurement: avoids direct contact with high-temperature rolled products, reduces interference, and is suitable for high-speed rolling scenarios (such as hot rolling line speeds of up to 10m / s or more).

[0050] Multi-area coverage: The array design can simultaneously measure multiple points (such as a 16×16 array) across the width of the rolled piece (e.g., 100-500mm range) to capture lateral differences in temperature distribution (such as the temperature difference between the edge and the center).

[0051] Accuracy and response: Temperature measurement accuracy is ±5°C, and response time can reach milliseconds (e.g. 10ms), adapting to dynamic temperature changes in high-speed rolling.

[0052] The roll assembly is driven by multiple independently controlled hydraulic servo units, with each set of rolls corresponding to a specific deformation zone of the workpiece (e.g., roughing, finishing, and thinning). The hydraulic servo system boasts high dynamic response (positioning accuracy ±0.01mm, response frequency >100Hz) and combined force / position control capabilities. By adjusting the roll gap, pressure, or rotational speed, it precisely controls the deformation and contact heat effects of the workpiece.

[0053] Furthermore, the system also includes a waste heat utilization module, integrated into the end of the variable-section rolling module. This module, consisting of a heat-insulating channel and shot peening device, utilizes the residual heat from rolling for in-line tempering and surface strengthening of the leaf springs. The heat-insulating channel is the transition zone after the rolled piece leaves the variable-section rollers. Its core function is to extend the high-temperature residence time of the rolled piece through thermal insulation design and controlled cooling strategies, maintaining the residual heat within the temperature range required for the tempering process.

[0054] Specifically, the running speed of the insulation channel is 0.1m / s~10m / s, the slow cooling speed is 0.1℃ / s~5℃ / s, and the temperature control range is 400℃~650℃.

[0055] Furthermore, it also includes a quality monitoring module, which is arranged at the end of the waste heat utilization module, performs real-time detection based on the cross-sectional profile of the leaf spring, and feeds back the data to the variable-section rolling module for correction.

[0056] In addition, the present invention also provides a short-process integrated production method for variable-section automobile leaf springs, comprising the integrated production system of the above embodiment and the following steps:

[0057] (1) Spring flat steel hot rolling stage: The steel is continuously rolled using rough rolling, intermediate rolling, finishing rolling and sizing mills. The rolling temperature is 800℃~1100℃ and the total deformation is 50%~95%;

[0058] (2) Online temperature control stage: Based on the outlet temperature of the spring flat steel sizing rolling, the cross-sectional dimensions of the rolled piece, the operating speed, and the starting temperature requirements of the variable cross-section rolling, online temperature calculation is performed, and different temperature control measures are taken to adjust the starting temperature of the spring flat steel variable cross-section rolling to the predetermined value;

[0059] (3) Variable cross-section rolling stage: adopt multi-pass asynchronous rolling process, the first pass rolling temperature is ≥950℃, the last pass rolling temperature is ≥650℃, and the total deformation is controlled at 50% to 85%;

[0060] (4) Residual heat treatment stage: by matching the rolling piece transmission speed, the leaf spring enters the residual heat utilization module within 10 seconds after rolling, and the tempering holding time is ≤60 seconds;

[0061] (5) Quality monitoring stage: Based on the real-time detection of the cross-sectional profile of the leaf spring, the data is fed back to the variable cross-section rolling stage for correction.

[0062] Furthermore, during the hot rolling stage of the spring flat steel, the thickness of the spring flat steel ranges from 8 mm to 50 mm.

[0063] Furthermore, in the variable-section rolling stage, the thickness of the variable-section leaf spring ranges from 0.5 mm to 25 mm, and the variable-section roller system in the variable-section rolling stage is continuously deformed ≥ 3 times.

[0064] Furthermore, during the variable cross-section rolling process, the temperature of the spring flat steel needs to be controlled. Under normal circumstances, the rolling temperature range is 800℃~1100℃, while during the variable cross-section rolling process, the first rolling temperature needs to be ≥950℃. In order to make the spring flat steel reach the appropriate temperature value, the spring flat steel needs to be temperature controlled by an online temperature control module. The electromagnetic heating device, the insulation track and the online cooling device in the present invention are independent of each other and can respectively realize heating or cooling of the spring flat steel so that the spring flat steel meets the temperature requirements of variable cross-section rolling. Specifically:

[0065] The heating speed of the electromagnetic heating device is 5℃ / s~200℃ / s.

[0066] The online controlled cooling device adopts online water cooling to reduce the temperature, and the cooling rate is 1℃ / s~50℃ / s.

[0067] The running speed of the insulation track is 0.1m / s~10m / s, and the slow cooling speed is 0.1℃ / s~5℃ / s.

[0068] Furthermore, during the hot rolling stage of the spring flat steel, when different specifications are rolled, the specification change time is ≤15 minutes.

[0069] Furthermore, the residual heat treatment stage includes multiple, sequentially decreasing temperature zones: the first zone is used for tempering the leaf spring, the second zone simultaneously performs laser cladding wear-resistant layer deposition or plasma nitriding, and the third zone implements high-pressure aerosol shot peening. The residual heat utilization module features a modular, detachable design, allowing for selection of process combinations such as "tempering + laser cladding wear-resistant layer deposition," "tempering + plasma nitriding," and "high-pressure aerosol shot peening" based on product requirements.

[0070] The temperature control range of the first temperature zone is 650℃~550℃. As the initial temperature control unit of the rolling production line (usually located in front of the variable-section rolling module), the temperature control range of the first temperature zone is set to 650℃~550℃. It is a key link to ensure that the rolled piece has a uniform and stable thermodynamic state before entering the deformation zone. At this temperature, the waste heat of the rolled piece is still sufficient to support online tempering. If the final temperature is too low (<500℃), the waste heat utilization module needs additional heating (such as electric heating), which increases energy consumption; if the final temperature is too high (>600℃), it is necessary to strengthen cooling (such as increasing the power of the air-cooling fan) to avoid waste heat.

[0071] The temperature control range of the second temperature zone is 550°C to 400°C. This zone is a critical link in the rolling process, connecting the previous and subsequent stages. Its core goal is to precisely control the temperature gradient of the rolled piece, balancing the material's plastic deformation capacity and deformation resistance, thereby providing stable thermodynamic conditions for the subsequent refined processing of variable-section rolling. The temperature control range of the third temperature zone is ≤400°C.

[0072] Furthermore, the steel type is any one of silicon-manganese spring steel, chrome-vanadium spring steel and silicon-chromium spring steel.

[0073] Example 1:

[0074] A short-process integrated production method for a variable-section automobile leaf spring is disclosed. The automobile leaf spring is rolled from a square billet of silicon-manganese spring steel 60Si2Mn to form an automobile leaf spring with a center thickness of 1.2 mm and a thickness of 0.5 mm at both ends. The method comprises the following rolling steps:

[0075] 1) Billets with a size of 160mm×225mm are cold-charged and then placed in a heating furnace and heated to 1100℃.

[0076] 2) After the roughing mill, intermediate rolling mill, finishing mill, and sizing mill, a spring flat steel with a thickness of 8 mm is obtained. The rolled piece temperature is 1050°C and the total deformation is 95.0%.

[0077] 3) Online temperature control stage: The rolled piece is cooled to 970°C through online water cooling;

[0078] 4) Variable cross-section rolling: Entering the variable cross-section rolling stage, 7 passes are rolled. During this period, the rolling force and rolling temperature parameters are monitored and the roll pressure and roll gap parameters are adjusted in real time during the variable cross-section rolling. The middle thickness is 1.2 mm, the thickness at both ends is 0.5 mm, and the deformation is 85.0%;

[0079] 5) Waste Heat Utilization Module: The rolled piece enters the waste heat utilization module at a temperature of 660°C. Tempering treatment is performed in the first temperature zone with a holding time of 60 seconds; laser cladding of a wear-resistant layer is performed in the second temperature zone; and high-pressure aerosol shot peening is performed in the third temperature zone.

[0080] 6) Quality monitoring: The leaf springs are sent to the finished product area after being qualified based on the thickness profile monitoring of the leaf spring section.

[0081] By adopting this production system and method, the process is over 30% shorter than traditional methods. Through three temperature zones for tempering, surface modification, and strengthening, waste heat utilization reaches over 85%, saving 40% to 50% energy compared to traditional processes that require additional heating furnaces. After variable-section rolling, the rolled piece enters the waste heat treatment stage within 10 seconds, effectively preventing grain boundary oxidation and increasing leaf spring fatigue life by ≥30%.

[0082] Example 2:

[0083] A short-process integrated production method for a variable-section automobile leaf spring is disclosed. The automobile leaf spring is rolled from a square billet of silicon-chromium spring steel 55SiCr to form an automobile leaf spring with a middle thickness of 13 mm and a thickness of 7 mm at both ends. The method comprises the following rolling steps:

[0084] 1) Billets with a size of 160mm×225mm are cold-charged and then placed in a heating furnace and heated to 1100℃.

[0085] 2) After the roughing mill, intermediate rolling mill, finishing mill, and sizing mill, a spring flat steel with a thickness of 20 mm is obtained. The rolled piece temperature is 960°C and the total deformation is 87.5%.

[0086] 3) Online temperature control stage: The rolled piece is slowly cooled to 950°C through a heat preservation cover;

[0087] 4) Variable cross-section rolling: Entering the variable cross-section rolling stage, three rolling passes are performed. During this period, the rolling force and rolling temperature parameters are monitored and the roll pressure and roll gap parameters are adjusted in real time during the variable cross-section rolling. The middle thickness is 13 mm, the thickness at both ends is 7 mm, and the deformation is 50.0%;

[0088] 5) Waste Heat Utilization Module: The rolled piece enters the waste heat utilization module at a temperature of 650°C. Tempering treatment is performed in the first temperature zone with a holding time of 55 seconds; laser cladding of a wear-resistant layer is performed in the second temperature zone; and high-pressure aerosol shot peening is performed in the third temperature zone.

[0089] 6) Quality monitoring: The leaf springs are sent to the finished product area after being qualified based on the thickness profile monitoring of the leaf spring section.

[0090] By adopting this production system and method, the process is over 30% shorter than traditional methods. Through three temperature zones for tempering, surface modification, and strengthening, waste heat utilization reaches over 85%, saving 40% to 50% energy compared to traditional processes that require additional heating furnaces. After variable-section rolling, the rolled piece enters the waste heat treatment stage within 10 seconds, effectively preventing grain boundary oxidation and increasing leaf spring fatigue life by ≥30%.

[0091] Example 3:

[0092] A short-process integrated production method for a variable-section automobile leaf spring is disclosed. The automobile leaf spring is rolled from a square billet of chrome-vanadium spring steel 50CrVA to form an automobile leaf spring with a middle thickness of 25 mm and a thickness of 16 mm at both ends. The method comprises the following rolling steps:

[0093] 1) Billets with a size of 160mm×225mm are cold-charged and then placed in a heating furnace and heated to 1100℃.

[0094] 2) After the roughing mill, intermediate rolling mill, finishing mill, and sizing mill, a spring flat steel with a thickness of 50 mm is obtained. The rolled piece temperature is 800°C and the total deformation is 68.5%.

[0095] 3) Online temperature control stage: The rolled piece is heated to 960°C through electromagnetic induction heating;

[0096] 4) Variable cross-section rolling: Entering the cross-section rolling stage, 5 passes were rolled. During this period, the rolling force and rolling temperature parameters were monitored and the roll pressure and roll gap parameters during variable cross-section rolling were adjusted in real time. The middle thickness was 25 mm, the thickness at both ends was 16 mm, and the deformation was 59.0%;

[0097] 5) Waste Heat Utilization Module: The rolled piece enters the waste heat utilization module at a temperature of 650°C. Tempering treatment is performed in the first temperature zone with a holding time of 60 seconds; plasma nitriding is performed in the second temperature zone; and high-pressure gas mist shot peening is performed in the third temperature zone.

[0098] 6) Quality monitoring: The leaf springs are sent to the finished product area after being qualified based on the thickness profile monitoring of the leaf spring section.

[0099] By adopting this production system and method, the process is over 30% shorter than traditional methods. Through three temperature zones for tempering, surface modification, and strengthening, waste heat utilization reaches over 85%, saving 40% to 50% energy compared to traditional processes that require additional heating furnaces. After variable-section rolling, the rolled piece enters the waste heat treatment stage within 10 seconds, effectively preventing grain boundary oxidation and increasing leaf spring fatigue life by ≥30%.

[0100] Example 4:

[0101] A short-process integrated production method for a variable-section automobile leaf spring is disclosed. The automobile leaf spring is rolled from a billet of chrome-vanadium spring steel 51CrV4 to form an automobile leaf spring with a middle thickness of 5 mm and a thickness of 3 mm at both ends. The method comprises the following rolling steps:

[0102] 1) Billets with a size of 160mm×225mm are cold-charged and then placed in a heating furnace and heated to 1100℃.

[0103] 2) After the roughing mill, intermediate rolling mill, finishing mill, and sizing mill, a spring flat steel with a thickness of 16 mm is obtained. The rolled piece temperature is 970°C and the total deformation is 90%.

[0104] 3) Online temperature control stage: the rolled piece is cooled to 955°C through air cooling;

[0105] 4) Variable cross-section rolling: Entering the variable cross-section rolling stage, 5 passes are rolled. During this period, the rolling force and rolling temperature parameters are monitored and the roll pressure and roll gap parameters are adjusted in real time during the variable cross-section rolling. The middle thickness is 5mm, the thickness at both ends is 3mm, and the deformation is 68.75%;

[0106] 5) Waste Heat Utilization Module: The rolled piece enters the waste heat utilization module at a temperature of 650°C. Tempering treatment is performed in the first temperature zone with a holding time of 55 seconds; plasma nitriding is performed in the second temperature zone; and high-pressure gas mist shot peening is performed in the third temperature zone.

[0107] 6) Quality monitoring: The leaf springs are sent to the finished product area after being qualified based on the thickness profile monitoring of the leaf spring section.

[0108] By adopting this production system and method, the process is over 30% shorter than traditional methods. Through three temperature zones for tempering, surface modification, and strengthening, waste heat utilization reaches over 85%, saving 40% to 50% energy compared to traditional processes that require additional heating furnaces. After variable-section rolling, the rolled piece enters the waste heat treatment stage within 10 seconds, effectively preventing grain boundary oxidation and increasing leaf spring fatigue life by ≥30%.

[0109] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. The short-process integrated production system for variable-section automobile leaf springs is characterized by: It includes an integrated hot rolling mill; The integrated hot rolling mill comprises a spring flat steel hot rolling module, an online temperature control module and a variable cross-section rolling module which are sequentially connected along the production line; The spring flat steel hot rolling module includes a heating furnace, a roughing mill, an intermediate rolling mill, a finishing mill and a reducing and sizing mill connected in sequence, and is used for continuous rolling of square billets; The online temperature control module is arranged at the rear side of the reducing and sizing unit and is used to adjust the starting rolling temperature of the spring flat steel variable cross-section rolling; The variable-section rolling module is composed of multiple groups of hydraulic servo rollers with adjustable roll gaps, and is used to continuously complete the variable-section rolling of leaf springs.

2. The short-process integrated production system for variable-section automobile leaf springs according to claim 1 is characterized in that: The online temperature control module includes an electromagnetic heating device, a heat preservation track and an online cooling control device; online temperature calculation is performed based on the outlet temperature of the spring flat steel sizing rolling, the cross-sectional dimensions of the rolled piece, the operating speed and the starting temperature requirements of the variable-section rolling, and temperature control is performed through the electromagnetic heating device or the heat preservation track or the online cooling control device to adjust the starting temperature of the spring flat steel variable-section rolling to a predetermined value.

3. The short-process integrated production system for variable-section automobile leaf springs according to claim 2 is characterized in that: The variable-section rolling module also includes an intelligent closed-loop control system, which includes a rolling force sensor and a temperature control sensor, which are used to display the roll pressure and roll temperature during variable-section rolling in real time, and transmit the sensor signal to the controller. The controller adjusts the rolling parameters of multiple groups of hydraulic servo rolls in the variable-section rolling module to form closed-loop control.

4. The short-process integrated production system for variable-section automobile leaf springs according to claim 3 is characterized in that: It also includes a waste heat utilization module, which is integrated at the end of the variable-section rolling module and includes a heat preservation channel and a shot blasting device, and utilizes the rolling waste heat to perform online tempering and surface strengthening treatment of the leaf spring.

5. The short-process integrated production system for variable-section automobile leaf springs according to claim 4 is characterized in that: It also includes a quality monitoring module, which is arranged at the end of the waste heat utilization module, and is based on real-time detection of the cross-sectional profile of the leaf spring, and feeds back the data to the variable-section rolling module for correction.

6. A short-process integrated production method for variable-section automobile leaf springs, characterized by: The method comprises the integrated production system according to claim 5 and the following steps: (1) Spring flat steel hot rolling stage: The steel is continuously rolled using rough rolling, intermediate rolling, finishing rolling and sizing mills. The rolling temperature is 800℃~1100℃ and the total deformation is 50%~95%; (2) Online temperature control stage: Based on the outlet temperature of the spring flat steel sizing rolling, the cross-sectional dimensions of the rolled piece, the operating speed, and the starting temperature requirements of the variable cross-section rolling, online temperature calculation is performed, and different temperature control measures are taken to adjust the starting temperature of the spring flat steel variable cross-section rolling to the predetermined value; (3) Variable cross-section rolling stage: adopt multi-pass asynchronous rolling process, the first pass rolling temperature is ≥950℃, the last pass rolling temperature is ≥650℃, and the total deformation is controlled at 50% to 85%; (4) Residual heat treatment stage: by matching the rolling piece transmission speed, the leaf spring enters the residual heat utilization module within 10 seconds after rolling, and the tempering holding time is ≤60 seconds; (5) Quality monitoring stage: Based on the real-time detection of the cross-sectional profile of the leaf spring, the data is fed back to the variable cross-sectional rolling stage for correction.

7. The short-process integrated production method for variable-section automobile leaf springs according to claim 6, characterized in that: During the hot rolling stage of the spring flat steel, the thickness of the spring flat steel ranges from 8 mm to 50 mm.

8. The short-process integrated production method for variable-section automobile leaf springs according to claim 6, characterized in that: In the variable cross-section rolling stage, the thickness of the variable cross-section leaf spring ranges from 0.5 mm to 25 mm, and the variable cross-section roller system in the variable cross-section rolling stage is continuously deformed for ≥3 times.

9. The short-process integrated production method for variable-section automobile leaf springs according to claim 6, characterized in that: During the online temperature control stage: The heating speed of the electromagnetic heating device is 5℃ / s~200℃ / s; The online controlled cooling device uses online water cooling to reduce the temperature, and the cooling rate is 1℃ / s~50℃ / s; The running speed of the insulation track is 0.1m / s~10m / s, and the slow cooling speed is 0.1℃ / s~5℃ / s.

10. The short-process integrated production method for variable-section automobile leaf springs according to claim 6, characterized in that: The residual heat treatment stage includes multiple temperature zones with successively lower temperatures. The first temperature zone is used for tempering the leaf spring, the second temperature zone simultaneously carries out laser cladding wear-resistant layer deposition or plasma nitriding process, and the third temperature zone implements high-pressure gas mist shot peening strengthening. The temperature control range of the first temperature zone is 650°C to 550°C; the temperature control range of the second temperature zone is 550°C to 400°C; and the temperature control range of the third temperature zone is ≤400°C.

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