CN112327970A - Control method for transition region strength of hot-forming variable-strength workpiece - Google Patents
Control method for transition region strength of hot-forming variable-strength workpiece Download PDFInfo
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- CN112327970A CN112327970A CN202010918577.6A CN202010918577A CN112327970A CN 112327970 A CN112327970 A CN 112327970A CN 202010918577 A CN202010918577 A CN 202010918577A CN 112327970 A CN112327970 A CN 112327970A
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
- G05D23/1917—Control of temperature characterised by the use of electric means using digital means
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05D—SYSTEMS FOR CONTROLLING OR REGULATING NON-ELECTRIC VARIABLES
- G05D23/00—Control of temperature
- G05D23/19—Control of temperature characterised by the use of electric means
- G05D23/20—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature
- G05D23/22—Control of temperature characterised by the use of electric means with sensing elements having variation of electric or magnetic properties with change of temperature the sensing element being a thermocouple
Abstract
A method for controlling the strength of a transition zone of a hot-forming variable-strength workpiece comprises the following steps: a. dividing the transition area into a plurality of subareas according to the hardness set value of each part on the workpiece; b. a temperature sensor and a group of electric heaters are arranged on the insert block corresponding to each subarea, the output end of each temperature sensor is connected with a controller, each group of electric heaters is provided with a contactor, and a control coil of the contactor is connected with the controller; c. determining an upper limit value and a lower limit value of the temperature according to the hardness set value range of each subarea; d. and controlling the working state of the corresponding electric heater according to the temperature measured value of each subzone temperature sensor, and controlling the temperature of the subzone within a set range. According to the invention, on the basis of partitioning the transition area of the workpiece, the insert temperature control system is used for carrying out closed-loop control on the temperature of each sub-area of the transition area, so that the temperature control precision is greatly improved, the linear change of the strength of the transition area of the product can be ensured, and the product quality is improved.
Description
Technical Field
The invention relates to a method for controlling the intensity of a transition region of a hot-forming variable-intensity workpiece, which can lead the intensity of the transition region of the workpiece to be linearly changed and belongs to the technical field of metal processing.
Background
The hot sheet metal phase change of the hot forming variable strength die is controlled by changing the temperature of the die insert block of the variable strength part, so that the hardness of the variable strength part is different from that of other parts. In order to ensure that the product has good energy absorption effect and meet the requirement of collision performance, the hardness of a transition region connected with a hard region and a soft region of the product is required to be changed linearly by each automobile manufacturer. However, the temperature control precision of the transition area is poor at present, so that the strength of the transition area of the product is difficult to ensure to be linearly changed, and the quality of the product cannot be ensured.
Disclosure of Invention
The invention aims to provide a method for controlling the strength of a transition area of a hot forming variable-strength workpiece, aiming at the defects of the prior art, so that the strength of the transition area of a product is changed linearly, and the quality of the product is improved.
The problems of the invention are solved by the following technical scheme:
a method of controlling the strength of a transition zone of a hot formed, strength-modified workpiece, the method comprising the steps of:
a. partitioning a transition area of the hot forming variable strength workpiece according to the hardness set value of each part on the workpiece, namely partitioning the part of the hardness set value in the same range into the same sub-area, thereby partitioning the transition area into a plurality of sub-areas;
b. the method comprises the following steps that a temperature sensor and a group of electric heaters are arranged on a die insert corresponding to each subarea of a transition area of the hot forming variable-strength workpiece, the output end of each temperature sensor is connected with the input end of a controller, each group of electric heaters is provided with a contactor, each group of electric heaters is connected with a power supply through a normally open contact corresponding to the contactor, and a control coil of the contactor is connected with the output end of the controller;
c. determining the upper limit value TH and the lower limit value TL of the temperature of each subarea in the hot forming process of the workpiece according to the hardness set value range of each subarea in the hot forming variable-strength workpiece transition area;
d. in the process of hot forming of the workpiece, the controller controls the working state of the corresponding electric heater through the contactor according to the temperature measurement value output by the temperature sensor corresponding to each subarea of the variable-strength workpiece transition area:
when the temperature measurement value output by the temperature sensor is smaller than the lower limit value TL, the controller enables the electric heater corresponding to the subarea to be electrified and heated; when the temperature measurement value output by the temperature sensor reaches the upper temperature limit value TH, the controller enables the electric heater corresponding to the subarea to stop heating;
thereby controlling the temperature of the sub-area within the range from TL to TH.
The method for controlling the strength of the transition region of the hot forming strength-variable workpiece specifically comprises the following steps:
a. setting the hardness set value of a soft area of the hot-forming variable-strength workpiece as Hr, setting the hardness set value of a hard area as Hh, and inserting n-1 hardness values between the Hr and the Hh: h1, H2, …, Hn-1, equally dividing the hardness interval (Hr, Hh) n;
b. drawing a curve formed by connecting points with a hardness set value of H1 in a transition area of the hot forming strength-changing workpiece to obtain a partition line corresponding to the hardness set value of H1; the division lines corresponding to the hardness set values H2, H3, … and Hn-1 are drawn in the same way to obtain n-1 division lines, and the n division lines divide the transition area of the hot forming variable strength workpiece into n sub-areas.
The method for controlling the strength of the transition region of the hot-forming variable-strength workpiece comprises the following specific steps of determining the upper temperature limit value TH and the lower temperature limit value TL of each sub-region in the hot-forming process of the workpiece:
a. obtaining a curve of the hardness of the workpiece along with the change of the thermal forming temperature through experiments;
b. and (3) setting the hardness set value range of a sub-zone of the hot forming strengthening workpiece transition zone as (Ha, Hb), calculating the average value of Ha and Hb, finding the temperature value T corresponding to the average value from the curve of the workpiece hardness changing along with the hot forming temperature, and setting a temperature change amount delta T, wherein the sub-zone temperature upper limit value TH is T + delta T, and the temperature lower limit value TL is T-delta T.
According to the method for controlling the strength of the transition region of the hot forming variable-strength workpiece, each group of electric heaters are uniformly distributed in the corresponding sub-region, the installation density of the electric heaters in different sub-regions is different, and the higher the temperature of the sub-region in the hot forming process of the workpiece is, the higher the installation density of the electric heaters is.
According to the method for controlling the strength of the transition region of the hot forming variable-strength workpiece, the diameter of the electric heater is less than 2 cm.
According to the method for controlling the strength of the transition region of the hot forming variable-strength workpiece, the temperature sensor is a thermocouple, and the temperature measuring end of the temperature sensor is positioned on the die insert and close to the die surface.
According to the method for controlling the strength of the transition region of the hot forming variable-strength workpiece, the controller is a single chip microcomputer or a microprocessor.
According to the invention, on the basis of partitioning the variable-strength workpiece transition area, the insert temperature control system consisting of the controller, the temperature sensor, the contactor and the electric heater is used for carrying out closed-loop control on the temperature of each sub-area of the workpiece transition area, so that the temperature control precision of the transition area is greatly improved, the linear change of the strength of the transition area of a product can be ensured, and the product quality is improved.
Drawings
The present invention will be described in further detail with reference to the accompanying drawings.
FIG. 1 is a schematic view of a transition zone of a hot formed strength-altered workpiece;
FIG. 2 is a schematic view of the mounting of an electric heater and temperature sensor on an insert;
FIG. 3 is an isometric view of the insert of FIG. 2;
fig. 4 is an electrical schematic of the insert temperature control system of fig. 2.
The reference numbers in the figures are: 1. the device comprises a workpiece, 2, an insert, U1, a controller, T1-T4, first-fourth temperature sensors, J1-J4, first-fourth contactors, R1-R4 and first-fourth groups of electric heaters.
Detailed Description
Aiming at the defects in the prior art, the invention provides a method for controlling the strength of a transition region of a hot-forming variable-strength workpiece, which comprises the following steps:
a. the transition area of the hot forming variable strength workpiece is divided according to the hardness set value of each part of the workpiece, namely, the part of the hardness set value in the same range is divided into the same subarea, so that the transition area is divided into a plurality of subareas, and the specific method comprises the following steps:
1) setting the hardness set value of a soft area of the hot-forming variable-strength workpiece as Hr, setting the hardness set value of a hard area as Hh, and inserting n-1 hardness values between the Hr and the Hh: h1, H2, …, Hn-1, the hardness interval (Hr, Hh) n is divided equally.
2) Drawing a curve formed by connecting points with a hardness set value of H1 in a transition area of the hot forming strength-changing workpiece to obtain a partition line corresponding to the hardness set value of H1; the division lines corresponding to the hardness set values H2, H3, … and Hn-1 are drawn in the same way to obtain n-1 division lines, and the n division lines divide the transition area of the hot forming variable strength workpiece into n sub-areas.
Taking the workpiece shown in fig. 1 as an example, the hardness set value of the soft region of the workpiece is Hr, the hardness set value of the hard region is Hh, and 3 hardness values are inserted between Hr and Hh: h1, H2, H3, equally divide the hardness range (Hr, Hh)4 into four hardness ranges: (Hr, H1), (H1, H2), (H2, H3), and (H3, Hh), and satisfies Hh-H3 ═ H3-H2 ═ H2-H1 ═ H1-Hr.
Since the boundary lines between the transition region and the soft and hard regions in fig. 1 are straight lines parallel to each other, the partition lines corresponding to H1, H2 and H3 are straight lines parallel to the boundary lines, and the partitioning result is shown in fig. 2, i.e., the transition region is divided into four sub-regions i, II, iii and iv, and in fig. 2, the left and right boundaries of the insert 2 are the boundary lines between the transition region and the soft and hard regions.
It should be noted that if the boundary lines between the transition region and the soft and hard regions are not straight lines parallel to each other, the partition lines corresponding to H1, H2, and H3 are not straight lines parallel to each other, and may even be curved lines.
b. The die insert is provided with a temperature sensor and a group of electric heaters at the position corresponding to each subarea of the transition area of the hot forming variable strength workpiece, the output end of each temperature sensor is connected with the input end of the controller, each group of electric heaters is provided with a contactor, each group of electric heaters is connected with the power supply through the normally open contact of the corresponding contactor, and the control coil of the contactor is connected with the output end of the controller.
In the present embodiment, the electric heater and the temperature sensor are mounted on the insert as shown in fig. 2 and 3, and the electric schematic diagram of the insert temperature control system is shown in fig. 4. In the figure, the first group of electric heaters R1 includes four electric heaters, the second group of electric heaters R2 and the third group of electric heaters R3 each include three electric heaters, and the fourth group of electric heaters R4 includes two electric heaters, i.e., the electric heaters in each sub-zone are installed at a density which gradually decreases from the soft zone to the hard zone. The temperature sensor is arranged at a position close to the die surface and used for detecting the temperature of the die surface.
c. Determining the upper limit value TH and the lower limit value TL of the temperature of each subarea in the hot forming process of the workpiece according to the hardness set value range of each subarea in the hot forming variable-strength workpiece transition area, wherein the specific method comprises the following steps:
1) obtaining a curve of the hardness of the workpiece along with the change of the thermal forming temperature through experiments;
2) and (3) setting the hardness set value range of a sub-zone of the hot forming strengthening workpiece transition zone as (Ha, Hb), calculating the average value of Ha and Hb, finding the temperature value T corresponding to the average value from the curve of the workpiece hardness changing along with the hot forming temperature, and setting a temperature change amount delta T, wherein the sub-zone temperature upper limit value TH is T + delta T, and the temperature lower limit value TL is T-delta T.
In this embodiment, Δ T is 10 ℃, the upper temperature limit TH and the lower temperature limit TL of sub-zone i are 400 ℃ and 380 ℃, respectively, the upper temperature limit TH and the lower temperature limit TL of sub-zone II are 300 ℃ and 280 ℃, respectively, the upper temperature limit TH and the lower temperature limit TL of sub-zone iii are 200 ℃ and 180 ℃, respectively, and the upper temperature limit TH and the lower temperature limit TL of sub-zone iv are 100 ℃ and 80 ℃, respectively.
d. In the process of hot forming of the workpiece, the controller controls the working state of the corresponding electric heater through the contactor according to the temperature measurement value output by the temperature sensor corresponding to each subarea of the variable-strength workpiece transition area:
when the temperature measurement value output by the temperature sensor is smaller than the lower limit value TL, the controller enables the electric heater corresponding to the subarea to be electrified and heated; when the temperature measurement value output by the temperature sensor reaches the upper temperature limit value TH, the controller enables the electric heater corresponding to the subarea to stop heating;
thereby controlling the temperature of the sub-area within the range from TL to TH.
In the embodiment, when the first temperature sensor T1 detects that the temperature of the insert is increased to 400 ℃, the first group of electric heaters R1 stops heating, and when the insert is cooled to 380 ℃, the group of electric heaters heat, and the temperature of the insert is kept to be about 390 ℃ and is close to the temperature of a soft zone; when the second temperature sensor T2 detects that the temperature of the insert is increased to 300 ℃, the second group of electric heaters R2 stops heating, and when the insert is cooled to 280 ℃, the group of electric heaters heat, and the temperature of the insert is kept at about 290 ℃; when the third temperature sensor T3 detects that the temperature of the insert is increased to 200 ℃, the third group of electric heaters R3 stops heating, and when the insert is cooled to 180 ℃, the group of electric heaters heat, and the temperature of the insert is kept at about 190 ℃; when the fourth temperature sensor T4 detects that the temperature of the insert rises to 100 ℃, the fourth group of electric heaters R4 stops heating, and when the insert is cooled to 80 ℃, the group of electric heaters heat, and the temperature of the insert is kept at about 90 ℃ and is close to the temperature of a hard area.
In order to ensure that the temperature of the transition region changes linearly, the width of the sub-region is as small as possible, when the partition lines on the two sides of the sub-region are mutually parallel straight lines, the electric heaters corresponding to the sub-region are arranged in a row, the center distance between the electric heaters in two adjacent sub-regions and the center distance between the electric heaters in the same sub-region are both less than 3 times of the diameter of a single electric heater, and the distance between the electric heater and the upper die surface of the die insert is greater than the center distance between the electric heaters, so that the local over-high temperature is prevented.
The higher the density of the electric heater, the more uniform the heating, therefore, the diameter of the electric heater should be as small as possible, in this embodiment, the diameter of the electric heater is less than 2 cm.
The temperature sensor is a thermocouple, and the temperature measuring end of the temperature sensor is positioned on the die insert and close to the die surface. The controller U1 is a single chip microcomputer or a microprocessor.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (7)
1. A method for controlling the strength of a transition zone of a hot forming variable strength workpiece is characterized by comprising the following steps:
a. partitioning a transition area of the hot forming variable strength workpiece according to the hardness set value of each part on the workpiece, namely partitioning the part of the hardness set value in the same range into the same sub-area, thereby partitioning the transition area into a plurality of sub-areas;
b. the method comprises the following steps that a temperature sensor and a group of electric heaters are arranged on a die insert corresponding to each subarea of a transition area of the hot forming variable-strength workpiece, the output end of each temperature sensor is connected with the input end of a controller, each group of electric heaters is provided with a contactor, each group of electric heaters is connected with a power supply through a normally open contact corresponding to the contactor, and a control coil of the contactor is connected with the output end of the controller;
c. determining the upper limit value TH and the lower limit value TL of the temperature of each subarea in the hot forming process of the workpiece according to the hardness set value range of each subarea in the hot forming variable-strength workpiece transition area;
d. in the process of hot forming of the workpiece, the controller controls the working state of the corresponding electric heater through the contactor according to the temperature measurement value output by the temperature sensor corresponding to each subarea of the variable-strength workpiece transition area:
when the temperature measurement value output by the temperature sensor is smaller than the lower limit value TL, the controller enables the electric heater corresponding to the subarea to be electrified and heated; when the temperature measurement value output by the temperature sensor reaches the upper temperature limit value TH, the controller enables the electric heater corresponding to the subarea to stop heating;
thereby controlling the temperature of the sub-area within the range from TL to TH.
2. The method for controlling the strength of the transition zone of the hot forming strength-variable workpiece as claimed in claim 1, wherein the specific method for partitioning the transition zone of the hot forming strength-variable workpiece is as follows:
a. setting the hardness set value of a soft area of the hot-forming variable-strength workpiece as Hr, setting the hardness set value of a hard area as Hh, and inserting n-1 hardness values between the Hr and the Hh: h1, H2, …, Hn-1, equally dividing the hardness interval (Hr, Hh) n;
b. drawing a curve formed by connecting points with a hardness set value of H1 in a transition area of the hot forming strength-changing workpiece to obtain a partition line corresponding to the hardness set value of H1; the division lines corresponding to the hardness set values H2, H3, … and Hn-1 are drawn in the same way to obtain n-1 division lines, and the n division lines divide the transition area of the hot forming variable strength workpiece into n sub-areas.
3. A method as claimed in claim 1 or claim 2, wherein the upper and lower temperature limits TH, TL of the sub-zones during the hot forming of the workpiece are determined by:
a. obtaining a curve of the hardness of the workpiece along with the change of the thermal forming temperature through experiments;
b. and (3) setting the hardness set value range of a sub-zone of the hot forming strengthening workpiece transition zone as (Ha, Hb), calculating the average value of Ha and Hb, finding the temperature value T corresponding to the average value from the curve of the workpiece hardness changing along with the hot forming temperature, and setting a temperature change amount delta T, wherein the sub-zone temperature upper limit value TH is T + delta T, and the temperature lower limit value TL is T-delta T.
4. The method of claim 3, wherein each set of electric heaters is uniformly distributed in the corresponding sub-area, the mounting density of the electric heaters in different sub-areas is different, and the higher the temperature of the sub-area during the thermal forming process of the workpiece, the higher the mounting density of the electric heaters.
5. The method of claim 4 wherein the electric heater has a diameter of less than 2 cm.
6. The method of claim 5, wherein the temperature sensor is a thermocouple, and the temperature measuring end of the temperature sensor is located on the die insert near the die face.
7. The method as claimed in claim 6, wherein the controller is a single chip or a microprocessor.
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| CN202010918577.6A CN112327970B (en) | 2020-09-04 | 2020-09-04 | Control method for transition region strength of hot-forming variable-strength workpiece |
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