CN113976683A - High-strength steel plate warm bending forming device and method for online local contact heating - Google Patents
High-strength steel plate warm bending forming device and method for online local contact heating Download PDFInfo
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- CN113976683A CN113976683A CN202111327616.6A CN202111327616A CN113976683A CN 113976683 A CN113976683 A CN 113976683A CN 202111327616 A CN202111327616 A CN 202111327616A CN 113976683 A CN113976683 A CN 113976683A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
- B21D5/008—Bending sheet metal along straight lines, e.g. to form simple curves combined with heating or cooling of the bends
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
- B21D5/002—Positioning devices
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
- B21D5/004—Bending sheet metal along straight lines, e.g. to form simple curves with program control
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D5/00—Bending sheet metal along straight lines, e.g. to form simple curves
- B21D5/02—Bending sheet metal along straight lines, e.g. to form simple curves on press brakes without making use of clamping means
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21D53/00—Making other particular articles
- B21D53/88—Making other particular articles other parts for vehicles, e.g. cowlings, mudguards
Abstract
A high-strength steel plate warm bending forming device and method for on-line local contact heating are disclosed, wherein the device comprises an upper die, a lower die assembly, a heating system and a temperature control system. The lower die component comprises a lower die, a side plate, a cross beam, an extension spring, a hanging nail and a connecting column; the heating system comprises a floating heating block, a ceramic insulating tube, an electric heating wire and a power line. Before bending, the beam is pulled upwards by an extension spring, and the initial position of the beam is limited by a limit pin; the floating heating block can move up and down along the vertical direction, and the upper surface of the floating heating block is 2-5 mm higher than the upper surface of the lower die before bending; when bending, the high-strength steel plate is placed on the lower die, and the bending position of the high-strength steel plate is heated by the electric heating wire penetrating through the ceramic insulating tube of the floating heating block. According to the method, the warm forming temperature is determined through the forming performance test of the high-strength steel plate at different temperatures. The invention can realize the on-line local accurate heating of the bending area, reduce the cracking probability, has small influence on the material structure performance and is suitable for mass production.
Description
Technical Field
The invention belongs to the field of metal plastic forming, and particularly relates to a high-strength steel plate warm bending forming device and method for on-line local contact heating.
Background
Plastic forming of metal can be classified into cold forming and hot forming according to whether it is heated or not. Strictly speaking, the temperature limit for distinguishing cold and hot forming is based on the recrystallization temperature of the metal (or austenitizing temperature of high strength steel), but since the recrystallization temperature (or austenitizing temperature) of most engineering metal materials is much higher than room temperature, plastic forming at room temperature is often referred to as cold forming. The cold forming does not need heating, and the precision and the surface quality of the finished piece are good, and generally the cold forming is preferably adopted. However, the problems of poor plastic deformation capability, high forming load, large springback and the like may exist during metal cold forming, and when the problems cannot be solved through a forming process and a die in actual production, hot forming can only be adopted. The hot forming can overcome the defects of poor deformation capability, high forming load and large rebound quantity of metal at normal temperature, but has low production efficiency, high cost and technical requirements, and a series of metallurgical changes can be generated on the organization structure of the metal at high temperature, so that the performance of a workpiece is reduced, the surface oxidation is serious and the processing precision is poor. For this reason, "warm forming" processes have been proposed in which the blank is heated to a temperature between the temperatures of cold and hot forming (or between room temperature and recrystallization temperature). Compared with cold forming, warm forming increases a heating link, but can increase the plasticity of the material to a certain extent, improve the forming capability, reduce the forming load and reduce the internal stress of the material; compared with hot forming, the method has the advantages of little influence on the structure, capability of shortening or omitting a heat treatment process, little tendency of surface oxidation and decarburization of a workpiece and longer service life of a die. But because the heating temperature is not high, the warm forming has limited improvement on the plastic deformation capacity of the material and reduction range of the forming load.
In recent years, in order to reduce the weight of a vehicle body and realize energy conservation and emission reduction, the application proportion of various high-strength steels in the field of automobiles is increasing day by day, and the strength index is also continuously improved. With the increase of the strength of the high-strength steel, the cold deformation capability of the high-strength steel is reduced sharply, so that the high-strength steel plate with the strength grade of over 1200MPa is generally subjected to hot forming at present, a proper material structure state is obtained through rapid cooling in a die after plastic deformation, and the technical requirement and the production cost are high. Due to the difference of the forming processes of different plates and the limitation of forming equipment, a large number of high-strength steel plate workpieces can only be formed by cold forming at room temperature. For example, bending is a common steel plate forming process, and since a bending deformation region only relates to a local position of a plate blank, the bending deformation region is not suitable for integral heating in a traditional heating furnace, and bending of high-strength steel plates is mostly performed in a cold state at present. However, with the continuous improvement of the strength level of the high-strength steel plate and the reduction of the plastic deformation capability, the probability of cracking in the bending production of the high-strength steel plate is continuously increased, and the yield is greatly influenced. In view of the integration of the advantages of cold and hot forming in warm forming, warm forming technology of high-strength steel plates has attracted attention in recent years, such as documents [ Longarmy peak, Zhaoyang, and the like ] research on warm forming performance of Docol1200M ultrahigh-strength steel plates, forging technology,2014, 39(2): 37-39; numerical simulation and experimental research of Wang Hui Min.22 MnB5 Steel plate warm forming limit, Yanshan university, Master academic paper, 2018; wangkedi, Lidy, et al, research on prediction of warm forming limit of advanced high strength steel DP780 slab, mechanical strength, 2021,43(5): 1177-. However, these studies mainly verify that warm forming can improve the plastic deformation capability of the material by methods such as tensile tests, and less relate to the specific sheet forming process. How to accurately and reliably heat the plate is the key to the success of warm forming. The above studies mainly use the heating technology of thermal forming, that is, the sheet is heated integrally by using thermal radiation in a heating furnace, and the sheet needs to be transferred to a mold for forming after being heated. Because the specific surface area of the plate is large and the heat dissipation is fast, the off-line heating mode in the furnace is difficult to accurately control the temperature of the plate for the warm forming with low self heating temperature. In addition, the heating energy loss in the furnace is large, the efficiency is low, the flexibility is poor, and the problems of changing the structure and the performance of an undeformed region, serious surface oxidation and the like exist. Therefore, some scholars propose a self-resistance heating mode by using current [ li-sialon, high-strength steel self-resistance heating process research, Hubei automobile industry academy, Master academic paper, 2017 ], but how to control the current and temperature of self-resistance heating in practical application has great difficulty. Considering that the heating temperature required for warm bending forming is relatively low and only local areas of bending deformation need to be heated, an infrared heating method is proposed by Lee et al [ EH Lee, J S Hwang, C W Lee, D Y Yang, W H Yang. Similar considerations are also addressed by Vorkov et al [ V Vorkov, A T Garc i a, J R Duflou. casting Parameters in Heat Assisted Air casting of High Strngth Steel. Procedia machining, 2020,47: 1314-. But heat the deformation zone of bending through the heat radiation, also difficult accurate control heating scope and temperature, and heating time is long, inefficiency, and practical value is limited. In addition, some researches adopt induction heating, but due to the fact that the shapes of plates are various and the sizes of the plates are large, an induction heating device is difficult to install, and the requirements of different processes are difficult to meet.
In summary, warm forming can improve the deformability of the high-strength steel plate during bending and reduce the cracking probability, but a suitable heating method needs to be developed to realize accurate and efficient heating of the bending deformation region.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a high-strength steel plate warm bending forming device and method for on-line local contact heating.
The high-strength steel plate warm bending forming device with on-line local contact heating is used for bending and forming a high-strength steel plate on a bending machine and comprises an upper die, a lower die assembly, and a heating system and a temperature control system which are installed on the lower die assembly.
The upper die of the high-strength steel plate warm bending forming device is the same as the upper die of a bending die used on the bending machine, and is connected with the upper sliding block of the bending machine in a working state.
The lower die assembly is arranged on a working table surface of the bending machine and comprises a lower die, a side plate, a cross beam, an extension spring, a hanging nail and a connecting column; the lower die is a strip-shaped block, a groove parallel to a bending line of the high-strength steel plate is formed in the middle of the upper surface of the lower die, two side plates are respectively attached to two end faces of the strip-shaped block, the side plates and the lower die are connected together through screws, and notches are formed in the middles of the side plates and in positions corresponding to the grooves of the lower die; the side plates are respectively provided with a horizontally placed strip-shaped cross beam relative to the outer side of the lower die, the strip-shaped cross beams are perpendicular to the bending line of the high-strength steel plate, two ends of each cross beam are respectively provided with a connecting column, the connecting columns are connected with the lower ends of vertically placed extension springs, and the upper ends of the extension springs are fixed on hanging nails inserted into the side plates; before bending and forming, on one hand, the cross beam is pulled upwards by the extension spring, and on the other hand, the two ends of the cross beam are blocked by the limiting nails arranged on the side plates from the upper part, so that the initial position of the cross beam is limited.
The heating system comprises a floating heating block, a ceramic insulating tube, an electric heating wire and a power line; the floating heating block is a strip-shaped block body with a rectangular cross section, chamfers are processed at four corners of the rectangular cross section, a through hole is processed in the middle of the rectangular cross section along the length direction of the strip-shaped block body, a cylindrical ceramic insulating tube is inserted into the through hole, and an electric heating wire penetrates through the ceramic insulating tube and is connected with a power line at one end of the ceramic insulating tube; the length of the floating heating block is greater than that of the lower die, and two ends of the floating heating block penetrate through a notch of a side plate of the lower die assembly and are fixed on a cross beam of the lower die assembly through screws; under the combined action of the cross beam and the extension spring, the floating heating block can move up and down along the vertical direction; before bending and forming, the upper surface of the floating heating block is 2-5 mm higher than the upper surface of the lower die.
When the bending forming is carried out, a power supply is switched on to enable the electric heating wire to generate heat, the heat of the electric heating wire is conducted to the floating heating block through the ceramic insulating tube, and the temperature of the floating heating block rises; measuring the temperature of the upper surface of the floating heating block by using an infrared thermometer, if the measured temperature reaches the temperature value for forming the high-strength steel plate, placing the high-strength steel plate to be bent on the lower die, and positioning the high-strength steel plate by using a positioning device of a bending machine; at this moment, the floating heating block is pressed down under the effect of the weight of the high-strength steel plate, the upper surface of the floating heating block descends to be flush with the upper surface of the lower die, and meanwhile, the floating heating block begins to heat the high-strength steel plate along the bending line nearby due to the fact that the lower surface of the high-strength steel plate is in contact with the upper surface of the floating heating block at the bending line position.
Measuring the upper surface temperature of the high-strength steel plate bending line position by using an infrared thermometer, recording the heating time from the placing of the high-strength steel plate to the time when the high-strength steel plate temperature forming temperature is reached and starting to bend and form if the temperature reaches the high-strength steel plate temperature forming temperature; at the moment, the bending machine controls the upper die to move downwards, the upper surface of the high-strength steel plate is pressed at the bending line position, and the high-strength steel plate is bent and deformed under the combined action of the upper die and the lower die; in the process, the upper surface of the floating heating block is pressed downwards by the high-strength steel plate, the floating heating block moves downwards and pulls the extension spring through the two cross beams, and the upper surface of the floating heating block is always attached to the lower surface of the high-strength steel plate under the combined action of the cross beams and the extension spring, so that the heat conduction can be stably carried out; when the upper die moves downwards to a set position, bending is finished, and the upper die returns upwards; under the action of the extension spring, the beam drives a heating system consisting of the floating heating block, the ceramic insulating tube, the electric heating wire and the power line to move upwards, and the beam and the heating system return to the initial position determined by the limit nails on the side plates and prepare for the next bending forming.
In order to accurately control the temperature of the floating heating block, a temperature sensor is arranged in the floating heating block, so that temperature data can be acquired in real time and transmitted into a temperature control system through a signal wire arranged on one side of the floating heating block; if the data transmitted by the temperature sensor is higher than the set value, the temperature control system cuts off the current of the power line, and the heating wire stops heating; if the data transmitted by the temperature sensor is lower than the set value, the temperature control system is connected with the power supply, and the electric heating wire heats, so that the temperature of the floating heating block is always kept in a determined range.
The high-strength steel plate warm bending forming method adopting online local contact heating comprises the following steps:
(1) gradually increasing from room temperature to the hot forming temperature of the high-strength steel plate according to the gradient of 50-100 ℃, and testing the forming performance of the high-strength steel plate at different temperatures to obtain a variation curve of the forming performance parameters of the high-strength steel plate along with the temperature; finding out the temperature with the maximum forming performance parameter as the reference heating temperature W for the warm forming of the high-strength steel plate;
the method for testing the forming performance of the material at different temperatures comprises a unidirectional stretching experiment and a bulging experiment, wherein the elongation after fracture at different temperatures is obtained through the unidirectional stretching experiment, and forming limit diagrams FLD at different temperatures are obtained through the bulging experiment;
(2) determining the power and the size of the electric heating wire according to the type and the thickness of the material of the high-strength steel plate to be bent and the length of a bending line; according to the size of the heating wire and the installation and use requirements of the bending machine, the design and the manufacture of the high-strength steel plate warm bending forming device are completed;
(3) mounting a high-strength steel plate warm bending forming device on a bending machine;
(4) the power supply of the power line is connected, and the electric heating wire heats the floating heating block; measuring the temperature of the upper surface of the floating heating block by using an infrared thermometer, recording data once per second, and acquiring the relationship between the temperature of the upper surface of the floating heating block and the heating time;
(5) when the upper surface temperature of the floating heating block reaches the reference heating temperature W, the heating time T from the time of turning on the power supply to the time is recorded0Placing the high-strength steel plate to be bent on the upper surface of the lower die, and positioning the high-strength steel plate by using a positioning device of a bending machine;
measuring the temperature of the middle position of the bending line on the upper surface of the high-strength steel plate by using an infrared thermometer, recording data once per second, and acquiring the relation between the temperature of the middle position of the bending line on the upper surface of the high-strength steel plate and the heating time;
(6) when the temperature value of the middle position of the upper surface bending line of the high-strength steel plate reaches the reference heating temperature W, recording the heating time T from the placing of the high-strength steel plate to the moment when the middle position of the upper surface bending line of the high-strength steel plate reaches the reference heating temperature W1(ii) a Starting a bending machine to bend and form, and when an upper die moves downwards to a preset position and bending is finished, returning the upper die and taking out a workpiece;
(7) placing the second high-strength steel plate to be bent on the upper surface of the lower die, positioning the high-strength steel plate by using a positioning device of a bending machine, and standing for T1Then, starting a bending machine to bend and form; when the upper die moves downwards to a preset position, bending is finished, the upper die returns, and a workpiece is taken out;
and repeating the steps until the forming of all high-strength steel plate workpieces is completed.
The invention has the following beneficial effects:
the invention can accurately and efficiently locally heat the bending deformation area of the high-strength steel plate, thereby meeting the requirement of high-strength steel plate bending forming at a high temperature and reducing the cracking probability of the deformation area; because the area near the fold line is only locally heated, the heat affected zone is small, and the heating temperature is below the recrystallization temperature, the mechanical property of the material is slightly influenced; the floating heating block is adopted to heat the high-strength steel plates in a contact manner, the characteristics of strong metal heat transfer capacity are utilized, the heating speed is high, the adjustable temperature range is wide, and the heating temperature can be accurately controlled, so that the bending requirements of different high-strength steel plate materials, thicknesses and bending angles are met; the whole device has simple mechanism, is easy to realize mechanization and automation and is suitable for mass production.
In addition, the bending deformation zone of the panel bend has the stress characteristics that the outer side (lower die side) is in tension and the inner side (upper die side) is in compression, so that the crack usually starts from the outer side. The floating heating block adopted by the invention starts to heat from the outer side of the high-strength steel plate, and keeps contact all the time in the bending process, so that good heating effect can be fully ensured.
Drawings
The invention is further described below with reference to the accompanying drawings and examples.
FIG. 1 is a schematic view of an initial state of the high-strength steel plate warm bending forming device with on-line local contact heating of the invention before bending forming;
FIG. 2 is a schematic view of the bending and forming process of the high-strength steel plate warm bending and forming device of the invention;
FIG. 3 is a side view of the high-strength steel plate warm bending forming device of the present invention during bending forming;
FIG. 4 is a flow chart of the warm bending forming method of the high-strength steel plate of the present invention;
FIG. 5 is a curve of the change of elongation after fracture of a Docol1200M high-strength steel plate along with temperature;
FIG. 6 is a cross-beam schematic view of the lower die assembly of the present invention;
FIG. 7 is a lower die schematic view of the lower die assembly of the present invention;
FIG. 8 is a schematic view of a floating heating block of the heating system of the present invention;
FIG. 9 is a schematic view of an upper die of the high-strength steel plate warm bending forming device of the present invention;
FIG. 10 is a side plate schematic of the lower die assembly of the present invention.
In the drawings 1-10, the following description is given,
1-side plate 2-hanging nail 3-extension spring 4-limit nail 5-beam 6-power line 7-electric heating wire 8-ceramic insulating tube 9-floating heating block 10-pin 11-screw 12-connecting column 13-lower die 14-high-strength steel plate 15-temperature sensor 16-upper die
Detailed Description
The invention will be further explained by taking the warm bending forming of the Docol1200M high-strength steel plate as an example. Docol1200M is a cold-rolled martensite high-strength steel produced by SSAB company, the yield strength is 1000MPa, and the tensile strength is 1200-1400 MPa.
In this embodiment, an on-line local contact heating bending forming device for a Docol1200M high-strength steel plate is shown in fig. 1 to 3.
In this embodiment, the on-line local contact heating warm bending forming method for the Docol1200M high-strength steel plate includes the following steps:
(1) and (3) performing forming performance tests on the Docol1200M high-strength steel plate at different temperatures in a gradient increasing mode at 100 ℃ from room temperature to the hot forming temperature of the Docol1200M high-strength steel plate to obtain a variation curve of forming performance parameters of the material along with the temperature.
In the embodiment, a unidirectional tensile experiment is adopted to measure the warm forming performance of the Docol1200M high-strength steel plate at different temperatures, and the elongation after fracture is taken as a forming performance parameter. According to the austenitizing temperature of the Docol1200M high-strength steel plate in hot forming, six test temperatures of room temperature, 100 ℃, 200 ℃, 300 ℃, 400 ℃ and 500 ℃ are selected for carrying out unidirectional tensile test, and the elongation after fracture of the material at different temperatures is obtained.
FIG. 5 shows the variation of elongation after fracture of Docol1200M high-strength steel plate with temperature. It can be seen that the elongation after fracture of Docol1200M gradually increases with increasing temperature, indicating that the temperature increases the plasticity of the material. However, the elongation after fracture between 200 ℃ and 300 ℃ is reduced, since in this temperature range the material is affected by the first type of temper embrittlement and blue embrittlement, there being medium temperature embrittlement zones. When the actual warm bending is formed, the heating temperature should be kept away from the range. When the temperature exceeds 300 ℃ and then reaches 500 ℃, the elongation after fracture rapidly increases along with the increase of the temperature, which indicates that the temperature in the range has great influence on the plasticity of the material. Although the temperature range of the maximum elongation after fracture is about 500 ℃ according to the experimental result, factors such as production cost, heating efficiency, material performance and surface quality are comprehensively considered, and the reference heating temperature of the Docol1200M high-strength steel plate for warm bending forming is finally determined to be 400 ℃ in the embodiment.
(2) The thickness of the Docol1200M high-strength steel plate to be bent and formed is 5mm, and the heating power of the electric heating wire is determined to be 1000 KW; according to the size of the heating wire and the installation and use requirements of a bending machine, the design and the manufacture of the Docol1200M high-strength steel plate warm bending forming device are completed;
(3) mounting the warm bending forming device on a bending machine;
(4) the power supply is switched on, and the electric heating wire heats the floating heating block; measuring the temperature of the upper surface of the floating heating block by using an infrared thermometer, recording data once per second, and acquiring the relationship between the temperature of the upper surface of the floating heating block and the heating time;
(5) when the temperature of the upper surface of the floating heating block reaches 400 ℃, recording the heating time T at the moment0Placing the high-strength steel plate to be bent on the upper surface of the lower die, and positioning the high-strength steel plate by a positioning device of a bending machine; the temperature of the position of the upper surface bending line of the high-strength steel plate is measured by using an infrared thermometer, data is recorded every second, and the relation between the temperature of the position of the upper surface bending line of the high-strength steel plate and the heating time is obtained.
(6) If the temperature value of the position of the bending line on the upper surface of the high-strength steel plate reaches 400 ℃, recording the heating time T at the moment1. Because the metal has strong thermal conductivity, the heating rate of the floating heating block to the Docol1200M high-strength steel plate can reach more than 50 ℃/s, so that the blank can be heated to 400 ℃ from room temperature within 10 s;
starting the bending machine to start forming, wherein the upper die moves downwards at the moment and enables the high-strength steel plate to generate bending deformation at the position of a bending line;
when the upper die moves downwards to a preset position, bending is finished, the upper die returns, and a workpiece is taken out;
(7) placing a second high-strength steel plate to be bent and formed on the upper surface of the lower die, positioning the second high-strength steel plate through a positioning device of a bending machine, and standing for a time T1Then, starting a bending machine to bend and form; when the upper die moves downwards to a preset position, bending is finished, the upper die returns, and a workpiece is taken out;
and repeating the steps until the bending and forming of all the high-strength steel plate workpieces are finished.
The high-strength steel plate warm bending forming device and the method for on-line local contact heating can efficiently and accurately locally heat a bending deformation area, meet the warm bending forming requirement of the high-strength steel plate, have small influence on the whole mechanical property of the material by a heat affected area, have high heating speed and wide heating temperature range, and are suitable for mass production.
The invention has not been described in detail in part in the common general knowledge of a person skilled in the art.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. The high-strength steel plate warm bending forming device is characterized by comprising an upper die, a lower die assembly, a heating system and a temperature control system, wherein the heating system and the temperature control system are installed on the lower die assembly.
2. The on-line local contact heating high-strength steel plate warm bending forming device according to claim 1, wherein an upper die of the high-strength steel plate warm bending forming device is the same as an upper die of a bending die used on a bending machine, and is connected with an upper slide block of the bending machine in a working state;
the lower die assembly is arranged on a working table surface of the bending machine and comprises a lower die, a side plate, a cross beam, an extension spring, a hanging nail and a connecting column; the lower die is a strip-shaped block, a groove parallel to a bending line of the high-strength steel plate is formed in the middle of the upper surface of the lower die, two side plates are respectively attached to two end faces of the strip-shaped block, the side plates and the lower die are connected together through screws, and notches are formed in the middles of the side plates and in positions corresponding to the grooves of the lower die; the side plates are respectively provided with a horizontally placed strip-shaped cross beam relative to the outer side of the lower die, the strip-shaped cross beams are perpendicular to the bending line of the high-strength steel plate, two ends of each cross beam are respectively provided with a connecting column, the connecting columns are connected with the lower ends of vertically placed extension springs, and the upper ends of the extension springs are fixed on hanging nails inserted into the side plates; before bending and forming, on one hand, the cross beam is pulled upwards by the extension spring, and on the other hand, the two ends of the cross beam are blocked by the limiting nails arranged on the side plates from the upper part, so that the initial position of the cross beam is limited.
3. The on-line local contact heating high-strength steel plate warm bending forming device according to claim 1, wherein the heating system comprises a floating heating block, a ceramic insulating tube, an electric heating wire and a power line; the floating heating block is a strip-shaped block body with a rectangular cross section, chamfers are processed at four corners of the rectangular cross section, a through hole is processed in the middle of the rectangular cross section along the length direction of the strip-shaped block body, a cylindrical ceramic insulating tube is inserted into the through hole, and an electric heating wire penetrates through the ceramic insulating tube and is connected with a power line at one end of the ceramic insulating tube; the length of the floating heating block is greater than that of the lower die, and two ends of the floating heating block penetrate through a notch of a side plate of the lower die assembly and are fixed on a cross beam of the lower die assembly through screws; under the combined action of the cross beam and the extension spring, the floating heating block can move up and down along the vertical direction; before bending and forming, the upper surface of the floating heating block is 2-5 mm higher than the upper surface of the lower die.
4. The high-strength steel plate bending and forming device with online local contact heating according to claim 1, wherein during bending, a power supply is switched on to heat the heating wire, the heat of the heating wire is conducted to the floating heating block through the ceramic insulating tube, and the temperature of the floating heating block rises; measuring the temperature of the upper surface of the floating heating block by using an infrared thermometer, if the measured temperature reaches the temperature value for forming the high-strength steel plate, placing the high-strength steel plate to be bent on the lower die, and positioning the high-strength steel plate by using a positioning device of a bending machine; at this moment, the floating heating block is pressed down under the effect of the weight of the high-strength steel plate, the upper surface of the floating heating block descends to be flush with the upper surface of the lower die, and meanwhile, the floating heating block begins to heat the high-strength steel plate along the bending line nearby due to the fact that the lower surface of the high-strength steel plate is in contact with the upper surface of the floating heating block at the bending line position.
5. The on-line local contact heating high-strength steel plate warm bending forming device according to claim 1, wherein an infrared thermometer is used to measure the temperature of the upper surface of the high-strength steel plate bending line, if the high-strength steel plate warm forming temperature is reached, the heating time from the placing of the high-strength steel plate to the reaching of the high-strength steel plate warm forming temperature is recorded, and the bending forming is started; at the moment, the bending machine controls the upper die to move downwards, the upper surface of the high-strength steel plate is pressed at the bending line position, and the high-strength steel plate is bent and deformed under the combined action of the upper die and the lower die; in the process, the upper surface of the floating heating block is pressed downwards by the high-strength steel plate, the floating heating block moves downwards and pulls the extension spring through the two cross beams, and the upper surface of the floating heating block is always attached to the lower surface of the high-strength steel plate under the combined action of the cross beams and the extension spring, so that the heat conduction can be stably carried out; when the upper die moves downwards to a set position, bending is finished, and the upper die returns upwards; under the action of the extension spring, the beam drives a heating system consisting of the floating heating block, the ceramic insulating tube, the electric heating wire and the power line to move upwards, and the beam and the heating system return to the initial position determined by the limit nails on the side plates.
6. The high-strength steel plate warm bending forming device adopting on-line local contact heating as claimed in claim 1, wherein a temperature sensor is installed inside the floating heating block, so that temperature data can be acquired in real time and transmitted into a temperature control system through a signal wire installed on one side of the floating heating block; if the data transmitted by the temperature sensor is higher than the set value, the temperature control system cuts off the current of the power line, and the heating wire stops heating; if the data transmitted by the temperature sensor is lower than the set value, the temperature control system is connected with the power supply, and the electric heating wire heats.
7. The high-strength steel plate warm bending forming method based on online local contact heating is characterized by comprising the following steps of:
(1) gradually increasing from room temperature to the hot forming temperature of the high-strength steel plate according to the gradient of 50-100 ℃, and testing the forming performance of the high-strength steel plate at different temperatures to obtain a variation curve of the forming performance parameters of the high-strength steel plate along with the temperature; finding out the temperature with the maximum forming performance parameter as the reference heating temperature W for the warm forming of the high-strength steel plate;
(2) determining the power and the size of the electric heating wire according to the type and the thickness of the material of the high-strength steel plate to be bent and the length of a bending line; according to the size of the heating wire and the installation and use requirements of the bending machine, the design and the manufacture of the high-strength steel plate warm bending forming device are completed;
(3) mounting a high-strength steel plate warm bending forming device on a bending machine;
(4) the power supply of the power line is connected, and the electric heating wire heats the floating heating block; measuring the temperature of the upper surface of the floating heating block by using an infrared thermometer, recording data once per second, and acquiring the relationship between the temperature of the upper surface of the floating heating block and the heating time;
(5) when the temperature of the upper surface of the floating heating block reaches the reference heating temperature W, placing the high-strength steel plate to be bent on the upper surface of the lower die, and positioning the high-strength steel plate by using a positioning device of a bending machine;
measuring the temperature of the middle position of the bending line on the upper surface of the high-strength steel plate by using an infrared thermometer, recording data once per second, and acquiring the relation between the temperature of the middle position of the bending line on the upper surface of the high-strength steel plate and the heating time;
(6) when the temperature value of the middle position of the upper surface bending line of the high-strength steel plate reaches the reference heating temperature W, recording the heating time T from the placing of the high-strength steel plate to the moment when the middle position of the upper surface bending line of the high-strength steel plate reaches the reference heating temperature W1(ii) a Starting a bending machine to bend and form, and when an upper die moves downwards to a preset position and bending is finished, returning the upper die and taking out a workpiece;
(7) placing the second high-strength steel plate to be bent on the upper surface of the lower die, positioning the high-strength steel plate by using a positioning device of a bending machine, and standing for T1Then, starting a bending machine to bend and form; when the upper die moves downwards to a preset position, bending is finished, the upper die returns, and a workpiece is taken out;
and repeating the steps until the forming of all high-strength steel plate workpieces is completed.
8. The method for testing the forming performance of the high-strength steel plate by online local contact heating is characterized by comprising a unidirectional stretching experiment and a bulging experiment.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117260137A (en) * | 2023-11-20 | 2023-12-22 | 矿冶科技集团有限公司 | Steel plate molding device and method for anchor cable connection |
| CN117299993A (en) * | 2023-11-28 | 2023-12-29 | 河北富华专用汽车制造有限公司 | Plate-shaped automobile part bending device |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN117260137A (en) * | 2023-11-20 | 2023-12-22 | 矿冶科技集团有限公司 | Steel plate molding device and method for anchor cable connection |
| CN117299993A (en) * | 2023-11-28 | 2023-12-29 | 河北富华专用汽车制造有限公司 | Plate-shaped automobile part bending device |
| CN117299993B (en) * | 2023-11-28 | 2024-02-20 | 河北富华专用汽车制造有限公司 | Plate-shaped automobile part bending device |
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