A straightening device and straightening method for hot-rolled steel bar wire rod tensile test specimen

Abstract

The present invention discloses a straightening device and method for hot-rolled steel bar wire rod tensile test specimens. The straightening device includes a frame, a power supply, and a servo driver and a PLC controller respectively connected to the power supply via lines. An electric cylinder is vertically arranged at the upper end of the frame. The input end of the electric cylinder is connected to a servo motor via a reducer. An upper pressure head is arranged at its output end. A lower pressure head is correspondingly arranged on the upper surface of the frame below the upper pressure head. The upper pressure head is provided with a pressure sensor. The pressure sensor and the servo driver are respectively connected to the PLC controller via lines. The servo motor is connected to the servo driver via lines. The application of the hot-rolled steel bar wire rod tensile test specimen straightening device and method provided by the present invention can ensure that the steel bar is not damaged or deformed on the basis of minimum plastic deformation when the wire rod tensile test specimen is straightened, thereby ensuring the accuracy of the wire rod tensile test results.

Description

Technical Field

[0001] The invention belongs to the technical field of straightening equipment, and in particular relates to a straightening device and a straightening method for a hot-rolled steel bar wire rod tensile test specimen. Background Art

[0002] The hot-rolled ribbed and round steel wire produced by the wire rolling mill (hereinafter referred to as hot-rolled steel wire rod) is delivered in coils and must undergo tensile testing before leaving the factory. The mechanical properties must meet the requirements of the standard or agreement before they can be shipped from the factory. The wire rod specimens removed from the coils are usually bent. Before the tensile test, simple bending straightening should be performed to ensure minimal plastic deformation, resulting in no obvious yield in the tensile curve, or even no yield behavior. In accordance with the requirements of the national standard GBT228.1-2021, for steel bars with unclear yield strength, the yield strength characteristic value adopts the specified plastic extension strength Rp. 0.2 , perform Rp on the wire sample 0.2 During the test, the specimen must be straightened first. When straightening the specimen, a rubber hammer, wooden hammer or special device is generally used to straighten it. On the basis of ensuring minimum plastic deformation, the axis of the specimen and the line of action of the force should be made to coincide with each other or be in the same plane. A non-straight specimen will result in an Rp error in the tensile test result. 0.2 The value is difficult to obtain and is prone to deviation. Excessive straightening can easily cause changes in mechanical and process properties. In actual straightening operations, it is difficult to straighten wire specimens to the required state using rubber hammers or wooden hammers. Especially with the increasing strength of hot-rolled steel wire rod, manual straightening using rubber hammers and wooden hammers is becoming increasingly difficult, and sometimes even impossible. The operator's labor intensity is also very high, and it is time-consuming and labor-intensive. Mechanical straightening using ordinary dedicated devices can easily cause wire deformation and damage, affecting the accuracy of tensile test results.

[0003] At present, the tensile specimens of hot-rolled steel wire rods are straightened by a hydraulic press. The force applied to the specimen during straightening by the hydraulic press is controlled by the stroke of the cylinder. When the operator sees that the cylinder pressure head contacts the specimen and the specimen has been straightened, he immediately releases the press switch to raise the press cylinder and separate it from the specimen. This device and straightening method place too high demands on the operator. The force applied to the wire rod specimen is uncontrolled, which can easily cause local deformation of the wire rod specimen and affect the tensile test results.

[0004] A search of relevant patents, literature and reports revealed few reports on straightening devices and methods for hot-rolled steel wire rods before tensile testing. There are many hot-rolled steel wire rod straightening or adjustment devices used on construction sites. However, these devices inevitably cause local deformation of the steel bars during the straightening process, affecting the tensile test results. Furthermore, these devices are only suitable for straightening entire coils of wire rods, and are not suitable for short specimens of about 500 mm taken from the coil for tensile testing.

[0005] Utility model patent CN202804021U discloses a laboratory round steel straightening machine, which includes a frame, an upper roller assembly, a lower roller assembly, and a transmission mechanism. The upper roller assembly includes an inlet pressure roller, multiple intermediate pressure rollers, and an outlet pressure roller. Each roller has the same diameter and its central axis lies in the same horizontal plane. The lower roller assembly includes an inlet support roller, multiple intermediate support rollers, and an outlet support roller. Each roller has the same diameter and its central axis lies in the same horizontal plane. The central axes of the multiple intermediate support rollers first gradually fall below the central axis of the inlet support roller and then gradually rise above the central axis of the inlet support roller. This round steel straightening machine can straighten high-strength, large-size steel bars, generates low stress during the straightening process, achieves high straightening accuracy, and can operate automatically and continuously. The round steel straightening machine uses a multi-roller straightening method to straighten round steel wire rods. It is necessary to manually adjust the position of the intermediate pressure wheel and the outlet pressure wheel to adjust the gap between the upper and lower rollers according to the different specifications of the wire rods. For round steels of different strengths, it is also necessary to adjust the gap between the upper and lower rollers to apply different forces to the round steel so that the round steel can be straightened. The operation is complicated and cannot be precisely controlled.

[0006] Utility model patent CN209363514U discloses a rebar straightening device with a simple structure, high efficiency, and uniform force distribution on rebar specimens. The device comprises a rectangular frame, a telescopic device, and a workbench. The rectangular frame is fixed to a base, and a telescopic device for squeezing is fixed vertically downward to the top beam of the rectangular frame. A pressure head is fixed to the telescopic rod of the telescopic device, and a workbench is located below the pressure head. This rebar straightening device places high demands on the straightening operator, and the force applied to the wire rod specimen is uncontrolled, which can easily cause local deformation of the wire rod specimen and affect the tensile test results.

[0007] From the above, it can be seen that the straightening of the hot-rolled steel bar wire tensile test specimen has become one of the key factors restricting the accuracy of the hot-rolled steel bar wire mechanical property test. Therefore, it is urgent to find a hot-rolled steel bar wire tensile test specimen straightening device that can make the specimen meet the requirements of the tensile test to the greatest extent on the basis of minimum plastic deformation. Summary of the Invention

[0008] In response to the technical problems existing in the background technology, the present invention provides a straightening device and a straightening method for hot-rolled steel bar wire rod tensile test specimens, which can ensure that the steel bars are not damaged or deformed on the basis of minimum plastic deformation when straightening the wire rod tensile test specimens, thereby ensuring the accuracy of the wire rod tensile test results.

[0009] The technical solution of the present invention to solve the technical problem is as follows:

[0010] The present invention discloses a straightening device for a hot-rolled steel bar wire rod tensile test specimen, which comprises a frame, a power supply, and a servo driver and a PLC controller respectively connected to the power supply through lines; an electric cylinder is vertically arranged at the upper end of the frame, an input end of the electric cylinder is connected to a servo motor through a reducer, an upper pressure head is arranged at the output end thereof, a lower pressure head is correspondingly arranged on the upper surface of the frame below the upper pressure head, a pressure sensor is arranged on the upper pressure head, the pressure sensor and the servo driver are respectively connected to the PLC controller through lines, and the servo motor is connected to the servo driver through lines.

[0011] Furthermore, the electric cylinder is provided with an upper limit magnetic switch and a lower limit magnetic switch, and the upper limit magnetic switch and the lower limit magnetic switch are respectively connected to the servo driver through lines.

[0012] Furthermore, the reducer is a planetary reducer.

[0013] Furthermore, V-shaped grooves are respectively provided on opposite sides of the upper pressing head and the lower pressing head, and the center lines of the two V-shaped grooves are in the same plane.

[0014] Furthermore, the surfaces of the upper pressure head and the lower pressure head are both circular.

[0015] Furthermore, the PLC controller is connected to a switch console via a line.

[0016] The present invention provides a straightening method for a hot-rolled steel bar wire rod tensile test specimen straightening device based on the above technical solution, comprising the following steps:

[0017] S1, placing the point to be straightened of the hot-rolled steel wire rod tensile test specimen on the lower pressure head;

[0018] S2, control the servo motor through the PLC controller so that the output end of the electric cylinder drives the upper pressure head to move downward;

[0019] S3, after the upper pressure head contacts the sample, it starts to apply the straightening force F, and transmits the detected straightening force signal to the PLC controller through the pressure sensor;

[0020] S4. When the straightening force F detected by the pressure sensor reaches the set value and continues for the straightening pressure holding time t, the PLC controller controls the servo motor to make the output end of the electric cylinder drive the upper pressure head to move upward and return to the set return position T1, ending a straightening action;

[0021] S5. If the sample has multiple straightening points, after completing one straightening action, replace the new straightening point on the lower pressure head, and then straighten it from the return position T1 according to steps S2 to S4. Repeat this cycle to complete the straightening action of each straightening point in turn until the straightening of the sample is completed.

[0022] Furthermore, suppose the length of the sample pushed each time during straightening is L; the position of the output end when the electric cylinder is not in action is T 复 , with T 复 As the origin, the position of the electric cylinder output end when the upper pressure head contacts the lower pressure head is T0. In each straightening action, the downward movement of the upper pressure head is divided into a no-load travel section and a straightening travel section. The position of the electric cylinder output end when the upper pressure head moves to the end of the no-load travel section is T2. The no-load travel speed and the straightening travel speed are V1 and V2 respectively. The return speed of the upper pressure head when it returns to the return position T1 after continuous straightening and holding time t is V3. The units of T0, T1, and T2 are mm, and the units of V1, V2, and V3 are mm / s; among them: T0>T2≥T1, T1 satisfies D≤T0-T1≤D+(0.5~2mm), and D is the nominal diameter of the hot-rolled steel bar, in mm; L satisfies 10mm≤L≤D1, unit is mm, R is the coil radius of the hot-rolled steel bar, unit is mm, D1 is the length of the V-groove of the upper pressure head (8), unit is mm; the straightening force F satisfies: (R eL ×S÷1000)<F<(R m ×S÷1000), the straightening force F is in KN; R eL is the nominal yield strength of hot-rolled steel bars, in MPa; R m is the nominal tensile strength of the hot-rolled steel bar, in MPa; S is the nominal cross-sectional area of ​​the hot-rolled steel bar, in mm 2 .

[0023] Furthermore, the no-load travel speed V1 and the return speed V3 are 10-40 mm / s, the straightening travel speed V2 is 0.5-1.0 mm / s, and the straightening holding time t is 0.3-1 s.

[0024] Furthermore, the no-load travel speed V1, return speed V3 and straightening holding time t are set in advance in the PLC controller, and the return position T1, no-load position T2, straightening force F and straightening travel speed V2 are set in advance in the PLC controller according to the strength grade of the sample to be straightened.

[0025] Compared with the prior art, the hot-rolled steel bar wire rod tensile test specimen straightening device and straightening method described in the present invention have the following beneficial effects:

[0026] (1) The straightening device described in the present invention has a novel and reasonable structure and is easy to manufacture and operate.

[0027] (2) The straightening device described in the present invention is a straightening device with pressure control, which can apply a set straightening force to the straightened sample, thereby effectively avoiding damage or deformation of the sample.

[0028] (3) The straightening device described in the present invention uses a servo motor to control the stroke and travel speed of the electric cylinder, with an accuracy of up to 0.01 mm, ensuring that the force applied to the straightened sample is accurate.

[0029] (4) The straightening device of the present invention is combined with its straightening method to set different straightening parameters according to different specifications and strengths of hot-rolled steel bars, and can automatically circulate straightening.

[0030] (5) The straightening device of the present invention, in conjunction with the straightening method thereof, can achieve multi-point straightening of the sample through the gap between the upper and lower pressure heads to ensure the straightness of the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic structural diagram of a straightening device for a hot-rolled steel bar wire rod tensile test specimen according to the present invention;

[0032] Figure 2 A schematic diagram of a method for straightening a hot-rolled steel wire rod tensile test specimen according to the present invention;

[0033] In the figure: 1. Frame; 2. Servo motor; 3. Reducer; 4. Electric cylinder; 5. Pressure sensor; 6. Upper limit magnetic switch; 7. Lower limit magnetic switch; 8. Upper pressure head; 9. Lower pressure head; 10. Servo drive; 11. PLC controller; 12. Power supply; 13. Switch console. DETAILED DESCRIPTION

[0034] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0035] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meanings understood by persons having ordinary skills in the field to which the present disclosure belongs. The terms "upper", "lower", "left", "right", "front", "back", etc. used in the patent application specification and claims of the present disclosure are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship also changes accordingly; "connected" or "connected" and similar terms are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect.

[0036] like Figure 1As shown, the present invention provides a straightening device for tensile test specimens of hot-rolled steel bar wire rods, which includes a frame 1, a power supply 12, and a servo drive 10 and a PLC controller 11 respectively connected to the power supply 12 through lines; the frame 1 is used to carry the entire straightening device, and an electric cylinder 4 is vertically arranged on its upper end. The electric cylinder 4 is a commonly used electric cylinder, and its input end is connected to a servo motor 2 through a reducer 3, and the reducer 3 can be a planetary reducer; the output end of the electric cylinder 4 is provided with an upper pressure head 8 with a V-groove, and the upper surface of the frame 1 below the upper pressure head 8 is correspondingly provided with a lower pressure head 9 with a V-groove. The surfaces on the opposite side of the upper pressure head 8 and the lower pressure head 9 are usually set to be circular, and the center lines of the two V-grooves are in the same plane; a pressure sensor 5 is tightly arranged on the upper pressure head 8 by a mechanical connection method, and the pressure sensor 5 and the servo drive 10 are respectively connected to the PLC controller 11 through lines, and the servo motor 2 is connected to the servo drive 10 through lines. The PLC controller 11 is used to receive relevant control commands, various sensor signals, and control the entire straightening device. The servo driver 10, also known as a "servo controller" or "servo amplifier," is a controller used to control a servo motor. Its function is similar to that of a frequency converter on a conventional AC motor. As part of a servo system, it is primarily used in high-precision positioning systems. It generally controls the servo motor using position, speed, and torque to achieve high-precision transmission system positioning. Currently, it is a high-end product in transmission technology. To facilitate control of the straightening device, the PLC controller 11 may also be connected to a switch console 13 via wiring. This console, for example, contains a start button and various switches for inputting relevant commands to the PLC controller.

[0037] In the above-mentioned straightening device, an upper limit magnetic switch 6 and a lower limit magnetic switch 7 can also be set on the electric cylinder 4. The upper limit magnetic switch 6 and the lower limit magnetic switch 7 are respectively connected to the servo driver 10 through lines to limit the extension and retraction stroke of the output end of the electric cylinder 4.

[0038] The straightening method of the hot-rolled steel wire rod tensile test specimen straightening device can be carried out according to the following steps:

[0039] S1, placing the point to be straightened of the hot-rolled steel wire rod tensile test specimen at the center of the V-groove on the lower pressure head 9;

[0040] S2. After the straightening device receives the start command (such as pressing the start button or foot switch), it sends a work command to the servo driver 10 through the PLC controller 11. The servo driver 10 drives the servo motor 2 to start working. The output end of the servo motor 1 is decelerated by the reducer 3 and drives the output end of the electric cylinder 4 to move downward, thereby driving the upper pressure head 8 installed at the output end of the electric cylinder 4 to move downward together;

[0041] S3, after the V-shaped groove of the upper pressure head 8 contacts the sample to be straightened placed on the lower pressure head 9, it starts to apply the straightening force F, and transmits the detected straightening force signal to the PLC controller 11 through the pressure sensor 5;

[0042] S4. When the straightening force F detected by the pressure sensor 5 reaches the set value and lasts for the straightening holding time t, the PLC controller 11 controls the servo motor 2 so that the output end of the electric cylinder 4 drives the upper pressure head 8 to move upward and return to the set return position T1, ending one straightening action;

[0043] S5. If the sample has multiple straightening points, after completing one straightening action, replace the new straightening point of the sample on the lower pressure head 9, and then straighten it from the return position T1 according to steps S2 to S4. Repeat this cycle to complete the straightening action of each straightening point in turn, and use the multi-point straightening method until the sample is straightened.

[0044] The straightening device can straighten the sample in a reciprocating manner with a single straightening action. Each time a straightening instruction is given to the PLC controller 11, the straightening device completes a straightening action. It can also automatically reciprocate and straighten. That is, after the straightening device receives the start instruction, it can repeat the above straightening action at a set time interval through the PLC controller, automatically reciprocate, and change the sample straightening point at the set time interval to achieve multi-point straightening without the need to issue a work start instruction in the middle.

[0045] More specifically, the above straightening method assumes that the output end position of the electric cylinder 4 is T when it is not in action. 复 , with T 复 As the origin, the position of the output end of the electric cylinder 4 when the upper pressure head 8 contacts the lower pressure head 9 is T0. In each straightening action, the upper pressure head 8 is divided into a no-load travel section and a straightening travel section when it moves downward. When the upper pressure head 8 moves to the end of the no-load travel section, the position of the output end of the electric cylinder is T2. The no-load travel speed and the straightening travel speed are V1 and V2 respectively. The return speed of the upper pressure head 8 to the return position T1 after continuous straightening and holding time t is V3. The units of T0, T1, and T2 are mm, and the units of V1, V2, and V3 are mm / s. T0>T2≥T1.

[0046] When designing the PLC control program for the straightening method, it was considered that different specifications and strength grades of hot-rolled rebar require different output end strokes and straightening forces for the electric cylinder. To avoid having to modify control parameters for each sample type, the straightening action can be designed into multiple PLC control programs with the same logic for straightening different sample types. Corresponding control buttons can be set on the switch controller 13 for inputting corresponding commands. Common parameters in the PLC control program, such as the no-load travel speed V1, return speed V3, and straightening hold time t, typically only need to be set once and do not require modification for different products. Individual parameters related to different products, such as the return position T1, no-load position T2, straightening force F, and straightening travel speed V2, can be set in each program.

[0047] When setting the control parameters of the straightening device, in order to ensure the convenience and speed of straightening and at the same time ensure that the steel bars are subjected to minimal plastic deformation, the control parameters must be set according to the following principles before straightening.

[0048] 1) Setting parameters such as no-load travel speed V1, return speed V3, and straightening pressure holding time t. These parameters affect the efficiency of the straightening operation. Under the premise that the straightening device allows, the no-load travel speed V1 and return speed V3 should be set as large as possible, generally between 10 and 40 mm / s. The straightening pressure holding time t does not need to be too long for hot-rolled steel bar straightening, generally between 0.3 and 1 second.

[0049] 2) Return position T1 setting. When the sample is straightened, the V-grooves on the upper pressure head 8 and the V-grooves on the lower pressure head 9 form an unclosed diamond hole. The sample is placed in the diamond hole with the bow facing upward. Since the sample is curved, the length of the sample pushed each time during straightening is L. The smaller the diamond hole, the smaller the length L of the sample pushed each time. The larger the diamond hole, the larger the pushing length L. The size of the diamond hole can be controlled by controlling the position of T1, and then the length L of the sample pushed each time can be controlled to achieve multi-point straightening. T1 should satisfy D≤T0-T1≤D+(0.5~2mm), where D is the nominal diameter of the hot-rolled steel bar in mm.

[0050] Propulsion length The length L should satisfy 10mm≤L≤D1, the unit is mm, R is the coil radius of the hot-rolled steel bar, the unit is mm, and D1 is the length of the V-groove of the upper pressure head 8, that is, its diameter, the unit is mm.

[0051] 3) Setting the no-load position T2. ​​When the specimen is straightened, the output end of the electric cylinder 4 moves to the no-load position T2. ​​The no-load travel speed V1 is converted to the straightening travel speed V2, and the speed becomes very slow. In order to shorten the time of each straightening action, it is necessary to ensure that the pressure head is as close to the specimen as possible at the no-load position T2, and the no-load position T2 ≥ the return position T1.

[0052] 4) Setting of straightening force F. The magnitude of straightening force F is related to whether the specimen can be straightened and whether deformation occurs. Straightening is actually a plastic deformation process, so the straightening force needs to be greater than the stress at which the hot-rolled steel bar yields, but less than the stress of the maximum uniform plastic deformation of the hot-rolled steel bar. The straightening force F should meet the following requirements: (R eL ×S÷1000)<F<(R m ×S÷1000), the straightening force F is in KN; R eL is the nominal yield strength of hot-rolled steel bars, in MPa; R m is the nominal tensile strength of the hot-rolled steel bar, in MPa; S is the nominal cross-sectional area of ​​the hot-rolled steel bar, in mm 2 .

[0053] 5) Setting the straightening travel speed V2. After the output end of the electric cylinder 4 travels to the no-load position T2 at speed V1, the no-load travel speed V1 is converted to the straightening travel speed V2. When the V-groove of the upper pressure head 8 contacts the specimen, a straightening force F is generated. The pressure sensor 5 detects the straightening force signal and transmits it to the PLC controller 11. When the actual straightening force reaches the set straightening force and the pressure is maintained for the set straightening holding time t, the output end of the electric cylinder 4 returns to the return position T1 at a return speed V3. During the straightening process of the sample, the straightening speed V2 should not be too large. If it is too large, the actual straightening force will rise too quickly, especially when the sample has been straightened. At this time, the straightening force will rise faster, and the PLC controller 11 will not have time to issue an instruction to stop the output end of the electric cylinder 4 and return, resulting in the applied straightening force instantly exceeding the set straightening force. The faster the speed, the greater the excess straightening force, which fails to achieve the purpose of straightening the sample according to the set force and easily causes deformation of the hot-rolled steel bar sample. Therefore, the straightening speed V2 is generally set to 0.5~1.0mm / s.

[0054] Before straightening the sample, select the corresponding straightening program for the sample according to the specifications and strength grade of the hot-rolled steel bars, confirm the straightening control parameters, and select the automatic control mode or the single straightening action reciprocating mode. Place one end of the sample with the bow facing upward in the V-groove of the lower pressure head, press the start button on the switch console, and the output end of the electric cylinder moves downward according to the straightening action described above to complete one straightening action. When the output end of the electric cylinder returns to the gap for the next downward movement, the sample is pushed forward to the required length or until it cannot be pushed forward anymore, and the straightening action is repeated. Repeat the cycle until the straightened length of the sample exceeds half of the total length of the sample. Then, rotate the sample 180° and start straightening from the other end until the entire sample is straightened.

[0055] The device and straightening method of the present invention can straighten hot-rolled steel wire rod tensile test specimens to meet the tensile test standard requirements, while maximally protecting the steel from deformation and ensuring the accuracy of the hot-rolled steel wire rod tensile test results. After straightening, the specimens exhibited a curvature of less than 2 mm per meter, superior to straight steel bars (GB T1499.2-2018 requires a curvature of no more than 4 mm per meter for hot-rolled straight steel bars), and exhibited no deformation.

[0056] The following is an example of straightening samples using the straightening device and straightening method of the present invention. The straightening sample specifications range from 6 mm to 14 mm, and the yield strength grades of hot-rolled steel wire rods range from 300 MPa to 635 MPa. The straightening effect is good. Specific examples are shown in Table 1 below.

[0057] Table 1 Implementation and application of the present invention

[0058]

[0059]

[0060] The T0 position was 66 mm, and the no-load travel speed V1, return speed V3, and straightening hold time t were uniformly set to 20 mm / s, 20 mm / s, and 0.5 s. The upper pressure head diameter D1 was 60 mm, and the coil radius R was 555 mm. The return position T1, propulsion length L, and straightening force F of Examples 1-7 all met the requirements of the present invention, as shown in Table 2.

[0061] Table 2 Implementation and application of the present invention

[0062] Example diameter Steel Type <![CDATA[T0-T1]]> Cross-sectional area S <![CDATA[R eL ]]> <![CDATA[R m ]]> <![CDATA[R eL ×S÷1000]]> <![CDATA[R m ×S÷1000]]> Propulsion length L unit mm - mm <![CDATA[mm 2 ]]> MPa MPa KN KN mm Example 1 6 HPB300 7.0 28.27 300 420 8.5 11.9 33.3 Example 2 6 HRB400E 7.0 28.27 400 540 11.3 15.3 33.3 Example 3 8 HRB400E 9.0 50.27 400 540 20.1 27.1 33.3 Example 4 10 HRB400E 10.5 78.54 400 540 31.4 42.4 23.6 Example 5 13.5 HWZ330 14.0 143.14 330 440 47.2 63.0 23.6 Example 6 6 HRB635 7.0 28.27 635 795 18.0 22.5 33.3 Example 7 10 HRB635 10.5 78.54 635 795 49.9 62.4 23.6

[0063] Note: R eL is the nominal yield strength of hot-rolled steel bars, R m is the nominal tensile strength of hot-rolled steel bars.

[0064] Judging from the straightness and deformation number of the straightened samples in the above embodiments, the straightening effect of the hot-rolled steel wire rod tensile test samples straightened by the straightening device and straightening method of the present invention is significantly better than that of the existing hydraulic press.

Claims

1. A straightening method for a straightening device for a hot-rolled steel bar wire rod tensile test specimen, the straightening device for a hot-rolled steel bar wire rod tensile test specimen comprising a frame (1), a power supply (12), and a servo driver (10) and a PLC controller (11) respectively connected to the power supply (12) via lines; an electric cylinder (4) is vertically arranged at the upper end of the frame (1), an input end of the electric cylinder (4) is connected to a servo motor (2) via a reducer (3), an upper pressure head (8) is arranged at the output end thereof, a lower pressure head (9) is correspondingly arranged on the upper surface of the frame (1) below the upper pressure head (8), a pressure sensor (5) is arranged on the upper pressure head (8), the pressure sensor (5) and the servo driver (10) are respectively connected to the PLC controller (11) via lines, and the servo motor (2) is connected to the servo driver (10) via lines, characterized in that: The straightening method is as follows: S1, placing the point to be straightened of the hot-rolled steel wire rod tensile test specimen on the lower pressure head (9); S2, controlling the servo motor (2) through the PLC controller (11) so that the output end of the electric cylinder (4) drives the upper pressure head (8) to move downward; S3, the upper pressure head (8) starts to apply the straightening force F after contacting the sample, and transmits the detected straightening force signal to the PLC controller (11) through the pressure sensor (5); S4, when the straightening force F detected by the pressure sensor (5) reaches the set value and continues for the straightening pressure holding time t, the PLC controller (11) controls the servo motor (2) so that the output end of the electric cylinder (4) drives the upper pressure head (8) to move upward and return to the set return position T1, thus ending a straightening action; S5. If the sample has multiple straightening points, after completing one straightening action, replace the sample with a new straightening point on the lower pressure head (9), and then straighten it from the return position T1 according to steps S2 to S4. This cycle is repeated to complete the straightening action of each straightening point in turn until the straightening of the sample is completed; Where: The length of the sample pushed each time during straightening is L; the position of the output end when the electric cylinder (4) is not in action is T 复 , with T 复 As the origin, the position of the output end of the electric cylinder (4) when the upper pressure head (8) contacts the lower pressure head (9) is T0. In each straightening action, the upper pressure head (8) is divided into an unloaded travel section and a straightening travel section in sequence when moving downward. The position of the output end of the electric cylinder (4) when the upper pressure head (8) moves to the end of the unloaded travel section is T2. The unloaded travel speed and the straightening travel speed are V1 and V2 respectively. The return speed of the upper pressure head (8) after the straightening and holding time t is V3 when it returns to the return position T1. The units of T0, T1, and T2 are mm, and the units of V1, V2, and V3 are mm / s. Among them: T0>T2≥T1, T1 satisfies D≤T0-T1≤D+(0.5~2mm), D is the nominal diameter of the hot-rolled steel bar, in mm; L= , L satisfies 10mm≤L≤D1, unit is mm, R is the coil radius of the hot-rolled steel bar, unit is mm, D1 is the length of the V-groove of the upper pressure head (8), unit is mm; the straightening force F satisfies: (R eL ×S÷1000)<F<(R m ×S÷1000), straightening force F in KN; R eL is the nominal yield strength of hot-rolled steel bars, in MPa; R m is the nominal tensile strength of the hot-rolled steel bar, in MPa; S is the nominal cross-sectional area of ​​the hot-rolled steel bar, in mm 2 .

2. The straightening method of the hot-rolled steel bar wire rod tensile test specimen straightening device according to claim 1, characterized in that: The no-load travel speed V1 and the return speed V3 are 10-40 mm / s, the straightening travel speed V2 is 0.5-1.0 mm / s, and the straightening holding time t is 0.3-1 s.

3. The straightening method of the hot-rolled steel bar wire rod tensile test specimen straightening device according to claim 2, characterized in that: The no-load travel speed V1, return speed V3 and straightening holding time t are set in advance in the PLC controller (11), and the return position T1, no-load position T2, straightening force F and straightening travel speed V2 are set in advance in the PLC controller (11) according to the strength grade of the sample to be straightened.

4. The straightening method of the hot-rolled steel bar wire rod tensile test specimen straightening device according to claim 1, characterized in that: An upper limit magnetic switch (6) and a lower limit magnetic switch (7) are provided on the electric cylinder (4), and the upper limit magnetic switch (6) and the lower limit magnetic switch (7) are respectively connected to a servo driver (10) through lines.

5. The straightening method of the hot-rolled steel bar wire rod tensile test specimen straightening device according to claim 1, characterized in that: The reducer (3) is a planetary reducer.

6. The straightening method of the hot-rolled steel bar wire rod tensile test specimen straightening device according to claim 1, characterized in that: The upper pressing head (8) and the lower pressing head (9) are respectively provided with V-shaped grooves on opposite sides thereof, and the center lines of the two V-shaped grooves are in the same plane.

7. The straightening method of the hot-rolled steel bar wire rod tensile test specimen straightening device according to claim 6, characterized in that: The surfaces of the upper pressure head (8) and the lower pressure head (9) are both circular.

8. The straightening method of the hot-rolled steel bar wire rod tensile test specimen straightening device according to claim 1, characterized in that: The PLC controller (11) is connected to a switch console (13) via a line.

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