On-line Detection Method and System for Baking Hardening Value of Cold-rolled Bake-Hardening High-Strength Steel

Abstract

The present invention discloses an on-line detection method and system for the bake hardening value of cold-rolled bake hardening high-strength steel. A set of electromagnetic parameter groups obtained by on-line measurement, the actual fluctuation value of the distance G between the strip steel and the electromagnetic detection unit, and the thickness of the current strip steel are used as inputs, and the bake hardening value is calculated through a unary linear regression statistical model. The present invention performs comprehensive electromagnetic detection on the running strip steel, obtains multiple electromagnetic signals in real time, simultaneously takes into account the correction of the distance affecting the electromagnetic parameters, and considers the influence of the strip steel thickness. The developed method does not depend on the process real-time parameters of the unit, and realizes the purpose of accurately measuring the bake hardening value of the strip steel on-line.

Description

Technical Field

[0001] The present invention relates to the technical field of non-destructive testing of steel plates, and more specifically, to an on-line detection method and system for the baking hardening value of cold-rolled bake hardening high-strength steel. Background Art

[0002] Bake hardening high-strength steel refers to retaining a certain amount of solid-solved carbon and nitrogen atoms in the steel, and at the same time, the strength can be increased by adding strengthening elements such as phosphorus and manganese. After processing and forming, and baking at a certain temperature, the yield strength of the steel further increases due to age hardening. The cold-rolled bake hardening high-strength steel plates and strips with a thickness of 0.5 mm to 2.5 mm are usually applied to automotive outer panels.

[0003] At present, domestic steel enterprises mainly use the method of cutting samples for off-line tests to detect the baking hardening value (BH2) of cold-rolled bake hardening steel, which is the method widely adopted at present. That is, samples are cut at a certain position of a coil of strip steel, such as the head and the tail, and then sent to the laboratory for off-line testing to obtain the baking hardening value of the sample, and thus the baking hardening value of a coil of strip steel is inferred. The existing measurement methods of the baking hardening value (BH2) are briefly introduced as follows:

[0004] 1) Specimen preparation: The size and sampling direction of the specimen shall comply with the regulations for mechanical property specimens.

[0005] 2) Test conditions: When measuring the baking hardening value, in accordance with the provisions of GB / T228, first perform a pre-tension of 2% total elongation on the specimen, and at the same time measure R t2.0 . After the specimen with 2% pre-tension has completed the specified heat treatment, perform a tensile test on the specimen again to measure R eL or R p0.2 .

[0006] In order to better maintain the consistency of test results, it is advisable to control the tensile speed in the form of displacement or strain, and it is recommended to set the tensile speed at a rate of 5% / min of the parallel length of the specimen. During the process from the start of tensile until the above indexes are measured, do not perform speed switching.

[0007] R t2.0 =F t2.0 / A0

[0008] R p0.2 =F p0.2 / A1

[0009] R eL =F eL / A1

[0010] Among them, F t2.0 : The tensile force (N) when the specimen is stretched and deformed to a total elongation of 2%;

[0011] F p0.2 : Tensile force when the non-proportional elongation of the specimen after heat treatment is 0.2% (when there is no obvious yield) (N);

[0012] F eL : Tensile force when the lower yield appears in the specimen after heat treatment (N);

[0013] A0: Original cross-sectional area of the specimen (mm 2 );

[0014] A1: Cross-sectional area of the specimen after 2% pre-strain (mm 2 ).

[0015] 3) Heat treatment conditions: After the temperature of the heating device reaches 170 °C, place the specimen that has undergone 2% pre-strain. After the heating device reaches 170 °C again, keep it warm for (20 ± 0.5) minutes. The temperature control accuracy is maintained at ±2 °C, and the resolution of the temperature measuring device does not exceed 1 °C at most. After heating, the specimen is cooled to room temperature in the air.

[0016] 4) Calculation of bake hardening value (BH2). The bake hardening value (BH2) is the difference between the lower yield strength of the specimen after baking or the yield strength corresponding to a non-proportional elongation of 0.2% (when there is no obvious yield) and the yield strength corresponding to a total elongation of 2% of the same specimen before baking. The schematic diagram for the calculation of BH2 is as Figure 1 shown, Figure 1 In which, the label 1 in Figure 1 is the stress-strain curve of 2% pre-strain, and the label 2 in

[0017] is the stress-strain curve of the same specimen after baking. The calculation formula is as follows: eL BH2 = R p0.2 (or R t2.0 )(after baking) - R t2.0 (before baking).

[0018] Advantages of the cut-specimen off-line test method are simplicity, direct results, and high precision. However, this method has the following disadvantages: First, there is a large data time lag, which is limited in helping the production process and impossible to achieve on-line control. Second, the data is incomplete and can only reflect the values at the head and tail of a coil of strip steel. Third, there is shear waste. When the unit is in production and stops or operates at a low speed due to certain reasons, in order to maintain the empirical judgment of "if the head and tail are qualified, then the middle is also qualified", usually a section of "suspected unqualified" strip steel needs to be cut off at this time. There is no judgment standard for how much to cut, and only as much as possible can be cut, which obviously causes waste. Fourth, it requires someone to work beside the machine all day long, with high labor intensity and high labor cost. Summary of the Invention

[0019] In view of the above defects in the prior art, the purpose of the present invention is to provide an on-line detection method and system for the baking hardening value of cold-rolled bake hardening high-strength steel. By applying comprehensive electromagnetic detection to the running strip steel, multiple electromagnetic signals are obtained in real time. At the same time, the correction of the spacing affecting the electromagnetic parameters is considered, and the influence of the strip steel thickness is considered. The developed method does not depend on the real-time process parameters of the unit, and realizes the purpose of accurately measuring the baking hardening value of the strip steel on-line.

[0020] To achieve the above purpose, the present invention adopts the following technical solutions:

[0021] In the first aspect of the present invention, an on-line detection method for the baking hardening value of cold-rolled bake hardening high-strength steel is provided:

[0022] On-line measure a set of electromagnetic parameters, the actual fluctuation value of the spacing G between the strip steel and the electromagnetic detection unit, and the thickness of the current strip steel;

[0023] According to a set of electromagnetic parameters, the actual fluctuation value of the spacing G, and the thickness, calculate the baking hardening value through a unary linear regression statistical model.

[0024] Preferably, the set of electromagnetic parameters includes tangent magnetic field harmonic detection response parameters, Barkhausen noise detection response parameters, incremental permeability detection response parameters, and multi-frequency eddy current detection response parameters.

[0025] Preferably, the tangent magnetic field harmonic detection response parameters include 11 electromagnetic parameters EM1-ME11;

[0026] The Barkhausen noise detection response parameters include 7 electromagnetic parameters EM12-ME18;

[0027] The incremental permeability detection response parameters include 7 electromagnetic parameters EM19-ME25;

[0028] The multi-frequency eddy current detection response parameters include 16 electromagnetic parameters EM26-ME41.

[0029] Preferably, the basic calculation of the baking hardening value BH2 is as follows:

[0030]

[0031] In the above formula, A is the constant term in the electromagnetic parameter regression equation, n is the number of samples, C i is the coefficient corresponding to each electromagnetic parameter, and X i is each set of electromagnetic parameters.

[0032] Preferably, when 2mm ≤ spacing G ≤ 6mm, the actual fluctuation value is input into the unary linear regression statistical model;

[0033] At this time, the calculation of the baking hardening value BH2 is a basic calculation plus a compensation calculation, which is specifically as follows:

[0034]

[0035] In the above formula, B is the compensation coefficient, and G is the actual measured value of the spacing;

[0036] When the spacing G > 6 mm or the spacing G < 2 mm, it is an abnormal state, and the detection is stopped.

[0037] The second aspect of the present invention provides an on-line detection system for the baking hardening value of cold-rolled bake-hardening high-strength steel, including:

[0038] An electromagnetic detection unit is arranged on a lifting device below the strip steel, and electromagnetic detection is performed on the strip steel to obtain a plurality of electromagnetic response signals;

[0039] A ranging instrument is arranged on the electromagnetic detection unit to obtain the spacing G between the lower surface of the strip steel and the electromagnetic detection unit;

[0040] A control computer is used to control the lifting and lateral movement of the lifting device. The unary linear regression statistical model in the control computer calculates the baking hardening value by obtaining the data of the electromagnetic detection unit and the ranging instrument;

[0041] The control computer also performs data interaction with the production computer;

[0042] The on-line detection method of the baking hardening value of the cold-rolled bake-hardening high-strength steel is realized by using the on-line detection system for the baking hardening value.

[0043] Preferably, a limiting device is further arranged on the lifting device.

[0044] The on-line detection method and system for the baking hardening value of the cold-rolled bake-hardening high-strength steel provided by the present invention can be used to perform on-line detection of the baking hardening value of the strip steel running on-line, obtain high-density data values of the entire length of the strip steel, and within the relative error accuracy range of 10%, the sample qualification rate is above 90%. It can also be comprehensively promoted to the on-line quality detection system for the baking hardening value of cold-rolled strip steel, realizing continuous detection, classification and recording of the production quality of steel plates, and playing a very positive role in improving production efficiency, product quality and product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 is a schematic diagram of the stress-strain curve;

[0046] Figure 2 is a schematic diagram of the calculation flow of the on-line detection method for the baking hardening value of the present invention;

[0047] Figure 3 It is a schematic framework diagram of the on-line detection system for the baking hardening value of the present invention;

[0048] Figure 4 It is a schematic diagram of the electromagnetic detection unit in the on-line detection system for the baking hardening value of the present invention in the measurement state;

[0049] Figure 5 It is a schematic diagram of the electromagnetic detection unit in the on-line detection system for the baking hardening value of the present invention in the non-measurement state;

[0050] Figure 6 It is a schematic diagram of the distribution of the baking hardening value in the full length direction of the strip steel in the embodiment of the on-line detection method for the baking hardening value of the present invention. Detailed implementation manners

[0051] In order to better understand the above technical solutions of the present invention, the technical solutions of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0052] Combined with Figure 2 As shown, an on-line detection method for the baking hardening value of a cold-rolled bake hardening high-strength steel provided by the present invention:

[0053] On-line measure a set of electromagnetic parameters, the actual fluctuation value of the distance G between the strip steel and the electromagnetic detection unit, and the thickness of the current strip steel, and calculate the baking hardening value through a unary linear regression statistical model according to the set of electromagnetic parameters, the actual fluctuation value of the distance G, and the thickness.

[0054] The set of electromagnetic parameters is the tangential magnetic field harmonic analysis detection response parameter, the Barkhausen noise detection response parameter, the incremental permeability detection response parameter, and the multi-frequency eddy current detection response parameter.

[0055] The output of each electromagnetic detection method is a curve signal. For the convenience of application, the curve signals of the above four electromagnetic detection results are further converted into several quantization parameters through definition, as shown in Table 1-4 below.

[0056] Table 1 Incentive magnetic field tangential magnetic field harmonic response parameters (a total of 11 items, EMi, i = 1,..., 11)

[0057]

[0058] Table 2 Barkhausen noise detection response parameters (a total of 7 items, EMi, i = 12,..., 18)

[0059]

[0060] Table 3 Incremental permeability electromagnetic detection response parameters (a total of 7 items, EMi, i = 19,..., 25)

[0061]

[0062]

[0063] Table 4 Multi - frequency Eddy Current Electromagnetic Detection Response Parameters (total 16 items, EMi, i = 20, ……, 41)

[0064]

[0065] In summary, the curve signals of the four electromagnetic detection results are transformed into at most 41 electromagnetic parameters through definition.

[0066] The basic calculation of the bake - hardening value BH2 is as follows:

[0067]

[0068] In the above formula, A is the constant term in the electromagnetic parameter regression equation, n is the number of samples, C i is the coefficient corresponding to each electromagnetic parameter, X i is each set of electromagnetic parameters.

[0069] Its evaluation criterion is: for a given number of samples n, the measurement accuracy of 90% of the samples satisfies a relative error ≤ 10%.

[0070] For the compensation of the spacing G between the strip steel and the electromagnetic detection unit, the compensation has an applicable range, which is specifically as follows:

[0071] When 2mm ≤ spacing G ≤ 6mm, the actual fluctuation value is input into the unary linear regression statistical model;

[0072] At this time, the calculation of the bake - hardening value BH2 is the basic calculation plus the compensation calculation, which is specifically as follows:

[0073]

[0074] In the above formula, A bh is the constant term in the electromagnetic parameter regression equation, with the unit of MPa, C i is the electromagnetic parameter, B bh is the weight coefficient of the fluctuation of the spacing G, with the unit of MPa / mm; in actual use, X i and G real are variables to achieve on - line measurement and calculation.

[0075] When the spacing G > 6mm or the spacing G < 2mm, it will cause large electromagnetic parameter deviations. At this time, it is an abnormal state and the detection is stopped.

[0076] Through data experiments and analysis, out of 44 electromagnetic parameters and 41 extended items of electromagnetic parameters, 12 electromagnetic parameters are obtained that can be used to calculate the R of the strip steel. p The 12 electromagnetic characteristic parameters are as follows in the table:

[0077] X EM device number EMi X1 EM1 A3 X2 EM3 A7 X3 EM9 <![CDATA[H co > X4 EM10 <![CDATA[H ro > X5 EM11 <![CDATA[V mag > X6 EM13 <![CDATA[M MEAN > X7 EM20 <![CDATA[U MEAN > X8 EM23 <![CDATA[DH25 U > X9 EM36 Mag3 X10 EM41 Ph4 X11 EM1’ A3 X12 EM2’ A5 X13 EM10’ <![CDATA[H ro > X14 EM22’ <![CDATA[H CU > X15 EM27’ Re2 X16 EM29’ Re4 X17 EM36’ Mag3 X18 EM41’ Ph4

[0078] And the obtained A bh 、B bh Are respectively: A bh =-126189.61, B bh =20.123, and the C coefficients corresponding to the electromagnetic parameter set X i Are shown in detail in the following table:

[0079]

[0080]

[0081] Combined with Figure 3 As shown, the strip steel 100 usually runs at a speed of 0 - 300 m / min. The strip steel 100 passes through two front and rear arranged idlers 200 to achieve a stable running trajectory line of the strip steel 100. The present invention also provides an on-line detection system for the baking hardening value of cold-rolled bake-hardening high-strength steel, including:

[0082] An electromagnetic detection unit 1, which is arranged below the strip steel 100 through a lifting device 2 and is located between two idlers 200. By performing electromagnetic detection on the strip steel 100, a plurality of electromagnetic signals are obtained;

[0083] A ranging instrument 3, which is arranged on the electromagnetic detection unit 1 to obtain the distance G between the lower surface of the strip steel 100 and the electromagnetic detection unit 1;

[0084] A control computer 4, which is used to control the lifting and lateral movement of the lifting device 2. The control computer 4 is equipped with a unary linear regression statistical model 401, a detection sensor unit controller 402, and a probe lifting and lateral movement control 403. By obtaining the measurement data of the electromagnetic detection unit 1 and the ranging instrument 3, the baking hardening value BH2 is finally calculated.

[0085] The control computer 4 also performs data interaction with the production computer 5 to obtain the production information of the current strip steel 100.

[0086] A limit device 6 is also arranged on the lifting device 2 to ensure the safety distance between the lower surface of the strip steel 100 and the electromagnetic detection unit 1.

[0087] Using this on-line detection system for the baking hardening value to realize the on-line detection method of the baking hardening value of cold-rolled bake-hardening high-strength steel.

[0088] The distance G between the lower surface of the strip steel 100 and the electromagnetic detection unit 1 is a key parameter. Due to external factors such as the jitter during the operation of the strip steel 100 and the fluctuations in the inherent plate properties of thin strip steel, the distance of the strip steel 100 fluctuates slightly. It is measured in real time by the distance measuring instrument 3, with a target value of 4 mm and an allowable fluctuation range of ±2 mm. This parameter is called Gap and serves as an input to the detection mathematical model. It should be particularly noted that when measuring the distance G, when 2 mm ≤ G ≤ 6 mm, the measurement is valid and the detection result can be corrected. For example, Figure 4 as shown, the electromagnetic detection unit 1 is in the measurement position; when G > 6 mm or G < 2 mm, the system is in an abnormal state, the detection conditions are not met, and the detection is invalid. For example, Figure 5 as shown, the electromagnetic detection unit 1 is in the non-measurement position.

[0089] Embodiment

[0090] The online detection method and system for baking hardening value of the present invention are applied to a production line for the online detection of a coil of strip steel. The steel grade of this coil of strip steel is 340BH, with a thickness of 0.7 mm, a width of 1585 mm, and a total length of 923.5 m for the strip steel. The online detection system has 382 outputs, that is, on average, one output per 2.5 meters. The calculation is as follows:

[0091]

[0092] Among them: Substitute A bh , the C coefficient, B bh value, and the input parameters X i and G obtained from real-time detection. The calculation results are as follows: Table of actual values, spacing values, and calculated values of Ae electromagnetic parameters:

[0093]

[0094] When the model is used for the real-time detection of a coil of strip steel, the detection results of the baking hardening value (BH2) in the full-length direction are as Figure 6 shown, which greatly improves the data volume and real-time performance compared with the prior art that can only test by shearing specimens.

[0095] Those of ordinary skill in the art in this technical field should recognize that the above embodiments are only used to illustrate the present invention and are not intended to limit the present invention. As long as it is within the scope of the substantial spirit of the present invention, changes and modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. An on-line detection method for the baking hardening value of cold-rolled bake-hardening high-strength steel, characterized in that: On-line measure a set of electromagnetic parameters, the actual measured value of the distance between the strip steel and the electromagnetic detection unit, and the thickness of the current strip steel; According to a set of electromagnetic parameters, the actual measured value of the distance, and the thickness, calculate the baking hardening value through a unary linear regression statistical model. The set of electromagnetic parameters includes tangential magnetic field harmonic detection response parameters, Barkhausen noise detection response parameters, incremental permeability detection response parameters, and multi-frequency eddy current detection response parameters. The tangential magnetic field harmonic detection response parameters include 11 electromagnetic parameters EM1-EM11; The Barkhausen noise detection response parameters include 7 electromagnetic parameters EM12-EM18; The incremental permeability detection response parameters include 7 electromagnetic parameters EM19-EM25; The multi-frequency eddy current detection response parameters include 16 electromagnetic parameters EM26-EM41. The basic calculation of the baking hardening value BH2 is as follows: In the above formula, A is the constant term in the electromagnetic parameter regression equation, n is the number of samples, and X i is each electromagnetic parameter, and C i is the coefficient corresponding to each electromagnetic parameter. When 2mm ≤ the actual measured value G of the distance ≤ 6mm, the actual measured value of the distance is input into the unary linear regression statistical model; At this time, the calculation of the baking hardening value BH2 is the basic calculation plus a compensation calculation, specifically as follows: In the above formula, B is the compensation coefficient and G is the actually measured value of the spacing; When the actual measured value G of the distance > 6mm or the actual measured value G of the distance < 2mm, it is an abnormal state, and the detection is stopped.

2. An on-line detection system for the baking hardening value of cold-rolled bake hardenable high-strength steel, characterized in that, It includes: An electromagnetic detection unit, arranged on a lifting device below the strip steel, and performing electromagnetic detection on the strip steel to obtain a plurality of electromagnetic response signals; A ranging instrument, arranged on the electromagnetic detection unit, for obtaining the distance between the lower surface of the strip steel and the electromagnetic detection unit; A control computer, used to control the lifting and lateral movement of the lifting device. The unary linear regression statistical model in the control computer calculates the baking hardening value by obtaining the data of the electromagnetic detection unit and the ranging instrument; The control computer also conducts data interaction with the production computer; Using the on-line detection system for the baking hardening value to implement the on-line detection method for the baking hardening value of the cold-rolled bake-hardening high-strength steel as described in claim 1.

3. The on-line detection system for baking hardening value of cold-rolled bake hardenable high-strength steel according to claim 2, characterized in that: A limiting device is also arranged on the lifting device.

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