A method for on-line control of plate shape warping in a stainless steel / carbon steel clad plate heat treatment process

Abstract

The application discloses a method for on-line control of plate shape warping in a stainless steel / carbon steel composite plate heat treatment process, which mainly comprises the following steps executed by a computer: 1. collecting basic equipment and process parameters of a heat treatment unit; 2. collecting parameters of the stainless steel / carbon steel composite plate; 3. defining relevant parameters and assigning initial values to the relevant parameters; 4. calculating internal stress σ(z) and strain ε of each material layer in process section i ij and calculating residual strain ΔE' of the process section i outlet ij ; 5. calculating a warping deformation amount control target function G(X) of the composite plate; 6. executing a judgment and a loop instruction; and 7. outputting tension control parameters σ yi and the minimum warping deformation amount G y of the composite plate. The application has small work load, improves the production efficiency of the composite plate heat treatment process, guarantees the requirement of a downstream process on high-quality plate shape to the maximum extent, and greatly improves the flexibility and intelligence of the composite plate heat treatment process production.

Description

Technical Field

[0001] This invention belongs to the field of heat treatment technology, and specifically relates to an online control method for the warpage of stainless steel / carbon steel composite plates during heat treatment. Background Technology

[0002] Stainless steel / carbon steel composite plates are made by bonding a stainless steel cladding layer with a carbon steel base layer through methods such as hot rolling, cold rolling, and explosive bonding. (See attached image) Figure 1 As shown, the prepared stainless steel / carbon steel composite plate needs to undergo heat treatment to enhance the interfacial bonding performance, improve the functionality of the metal layer, and eliminate residual stress. [1] During the preparation and heat treatment processes, due to the differences in mechanical properties and thermodynamic parameters between the dissimilar metal layers of the composite plate, as well as the influence of process parameters during hot rolling and explosive bonding, varying degrees of elasto-plastic deformation often occur between the base layer and the cladding layer. This interlayer incoordination generates internal stress, leading to internal couples that cause the composite plate to bend, resulting in undesirable morphologies such as plate warping. In severe cases, this can affect subsequent processing and forming. In current production practice, to ensure that the finished stainless steel / carbon steel composite plate has the correct shape and dimensions, production personnel often introduce a straightening process. Between the rotating straightening rollers of the straightening machine, the plate is bent multiple times to eliminate the original curvature. After multiple roller straightening processes, the original curvature gradually decreases, and the plate gradually becomes straight. [2] This process uses forced bending to induce plastic deformation in the composite board to improve its shape. However, when the warping deformation is too large or the composite board is too rigid, it often fails to straighten properly. Furthermore, the straightening process often introduces additional internal plastic stress and strain into the board, which can affect its mechanical properties to some extent. Therefore, minimizing warping during the initial heat treatment process and reducing the burden on the subsequent straightening process has become a key issue in composite board production.

[0003] During heat treatment, changes in the shape of stainless steel / carbon steel composite plates are an objective reality, which on-site technicians are well aware of. However, the available adjustment methods are limited and relatively haphazard, failing to achieve effective results. Furthermore, the shape changes during heat treatment are a coupling of multiple factors, including the internal and external temperature differences of the composite plate, microstructural phase transformations, composite material parameters, and processing parameters. Existing control technologies can only determine the quality of control based on the final finished plate shape, and even then, timely adjustments cannot be made regardless of success. Moreover, the incoming plate shape and heat treatment parameters for each composite plate are unique, making adjustments between different plates unreliable.

[0004] According to the existing public documents, the plate shape warping control technology for the heat treatment process of stainless steel / carbon steel composite plate has not yet appeared. Therefore, how to realize the online control of the plate shape warping of the stainless steel / carbon steel composite plate in the production of the heat treatment process, and reduce the burden of the downstream straightening unit of the production line, has become the research focus of the relevant technical personnel of the heat treatment.

[0005] REFERENCES

[0006] [1] Huang Wei. Stainless steel / carbon steel layered structure composite plate production process [J]. Science and technology and enterprise, 2014 (05): 274-275.

[0007] [2] Liu Baolong. Interface microstructure and performance of hot-rolled wide and thick stainless steel composite plate and rolling process research [D]. Yanshan University, 2017. SUMMARY

[0008] In order to overcome the deficiencies in the prior art, the present application provides a stainless steel / carbon steel composite plate heat treatment process plate shape warping online control method, which is based on the heat treatment production line automatic control system, and adopts mathematical model online adjustment to accurately control the composite plate shape, so that the plate shape of the stainless steel / carbon steel composite plate after heat treatment is effectively guaranteed, the burden of the subsequent leveling unit is reduced, the production efficiency is improved, and the production application value is high.

[0009] The present application comprises the following steps executed by computer:

[0010] (a) Collect the basic equipment and process parameters of the heat treatment unit, mainly including: the total number of process sections of heat treatment is 3, define the process section number {i, i=1, 2, 3}; Collect the maximum value σ zi,max , the minimum value σ zi,min , the temperature T i at the end of the process section i, the initial temperature T0 of heat treatment;

[0011] (b) Collect the parameters of stainless steel / carbon steel composite plate, mainly including: the original length L, the total thickness h, the width b, the thickness ratio λ of stainless steel / carbon steel composite plate, the material layer j of stainless steel / carbon steel composite plate is numbered 1, 2 in turn (1-stainless steel cladding layer, 2-carbon steel base layer), the thickness h j of each material layer, the elastic modulus E i of each material layer in the elastic deformation stage when the temperature of each process section is T ij , the elastic modulus E' ij of the strengthening stage, the initial residual strain Δε 0j of incoming material, the linear expansion coefficient β ij , the yield strength σ sij , the initial value G0 of the composite plate shape warping control target function;

[0012] (c) define relevant parameters, mainly including: internal stress σ(z) distributed along the thickness direction, total strain ε ij , elastic strain ε eij , residual strain Δε ij at the inlet of process section i, residual strain Δε' ij at the outlet of process section i, initial residual strain Δε 0j of incoming material, set tension σ zi of each process section, tension adjustment step Δσ; length L' of the clad plate during heat treatment, interlayer bending moment M r ; distance δ between the strain neutral layer and the interface layer of the clad plate, corresponding central angle 2θ of the clad plate after bending, curvature radius R, plate shape warping control objective function G(X), tension control parameters σ yi of each process section, optimal value G y of the plate shape warping of the clad plate; tension adjustment parameters k, m, n;

[0013] (d) assign initial values to relevant parameters: let i = 1, k = 0, m = 0, n = 0, set tension adjustment step Δσ, let Δε 1j = Δε 0j (j = 1, 2), let σ zi = σ zi,min , give initial value G0 of the objective function, let G y = G0;

[0014] (e) let σ z1 = σ z1 +k*Δσ; update loop variable;

[0015] (f) let σ z2 = σ z2 +m*Δσ; update loop variable;

[0016] (g) let σ z3 = σ z3 +n*Δσ; update loop variable;

[0017] (h) calculate internal stress σ(z) and strain ε ij of each material layer in process section i;

[0018]

[0019] (i) calculate residual strain Δε' ij at the outlet of process section i;

[0020]

[0021] (j) judge whether the inequality i < 3 is true, if the inequality is true, let Δε ij = Δε'ij , i = i + 1, go to step (h); if the inequality is not true, go to step (k);

[0022] (k) calculate the plate shape warping amount control target function G(X) of the composite plate;

[0023] G(X) = [R + δ - h(λ - 1)](1 - cosθ)

[0024] wherein:

[0025] (l) judge whether G(X) < G y is true? If the inequality is true, record the tension control parameter and the plate shape warping amount of the composite plate, let σ yi = σ zi , G y = G(X), go to step (m), otherwise, go to step (m) directly;

[0026] (m) judge whether σ z3 < σ z3,max is true? If the inequality is true, let n = n + 1, go to step (g); otherwise, go to step (n);

[0027] (n) judge whether σ z2 < σ z2,max is true? If the inequality is true, let m = m + 1, go to step (f); otherwise, go to step (o);

[0028] (o) judge whether σ z1 < σ z1,max is true? If the inequality is true, let k = k + 1, go to step (e); otherwise, go to step (p);

[0029] (p) output the tension control parameter σ yi of each process section and the minimum plate shape warping amount G y of the composite plate;

[0030] Compared with the prior art, the present application has the following advantages:

[0031] The workload is small, and the plate shape warping online control in the heat treatment process of the stainless steel / carbon steel composite plate is realized without increasing the hardware investment cost and without large-scale modification of the hardware, the production efficiency of the heat treatment process of the composite plate is improved, the requirement of the downstream process for high-quality plate shape is ensured to the greatest extent, and the flexibility and intelligence of the production of the heat treatment process of the composite plate are greatly improved. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is a common stainless steel / carbon steel composite plate production process flow chart.

[0033] Figure 2 Fig. 1 is a schematic diagram of the warping deformation of the composite plate.

[0034] Figure 3 Fig. 1 is a schematic diagram of the warping deformation of the composite plate.

[0035] Figure 4 Fig. 1 is a schematic diagram of the warping deformation of the composite plate.

[0036] Figure 5 Fig. 1 is a schematic diagram of the warping deformation of the composite plate. DETAILED DESCRIPTION

[0037] Example 1

[0038] Fig. 1 is a schematic diagram of the warping deformation of the composite plate. Figures 3-4 Taking the 316L / Q235 composite plate with the specification of 1000*500*40 mm and the solid solution heat treatment process at 1100℃ as an example, the online control method for the plate shape warping in the heat treatment process of the stainless steel / carbon steel composite plate proposed in the present application is further described, and the execution flow thereof is shown in Fig. 1. Figure 3

[0039] In step (a), the basic equipment and process parameters of the heat treatment unit are collected. Mainly including: the total number of process sections is 3, the process section number {i, i=1, 2, 3} is defined; the maximum value of the allowable set tension in each process section is collected σ z1,max =10 MPa, σ z2,max =15 MPa, σ z3,max =10 MPa; the minimum value is σ z1,min =0 MPa, σ z2,min =0 MPa, σ z3,min =0 MPa, the temperature T1 at the end of process section 1 is 1100℃, the temperature T2 at the end of process section 2 is 1100℃, the temperature T3 at the end of process section 3 is 25℃, and T0 is 25℃.

[0040] Subsequently, in step (b), the parameters of the 316L / Q235 composite plate are collected, mainly including: the original length L=1000 mm, the total thickness h=40 mm, the cladding thickness h1=10 mm, the base layer thickness h2=30 mm, the width b=400 mm, the thickness ratio λ=0.25, the material layers j of the 316L / Q235 composite plate are numbered 1 and 2 in turn (1-316L cladding layer, 2-Q235 base layer), and the temperature of each process section is T i , the elastic modulus E ij , the strengthening stage elastic modulus E' ij , the initial residual strain Δε 0j , the linear expansion coefficient β ij , the yield strength σ sij ​G0, the initial value of the target function of the plate shape warping amount control of the clad plate;

[0041] Then, in step (c), the relevant parameters are defined, mainly including: the internal stress σ(z) distributed along the thickness direction, the total strain ε ij , the elastic strain ε eij , the residual strain Δε ij at the inlet of the process section i, the residual strain Δε' ij at the outlet of the process section i, the initial residual strain Δε 0j of the incoming material, the set tension σ zi of each process section, the tension adjustment step Δσ; the length L' of the clad plate during the heat treatment process, the interlayer bending moment M r ; the distance δ between the strain neutral layer and the interface layer of the clad plate, the corresponding central angle 2θ of the clad plate after bending, the radius of curvature R, the target function G(X) of the plate shape warping amount control of the clad plate, the tension control parameter σ yi of each process section, the optimal value G y of the plate shape warping amount of the clad plate; the tension adjustment parameters k, m, n;

[0042] Then, in step (d), the relevant parameters are assigned initial values: let i = 1, k = 0, m = 0, n = 0, set the tension adjustment step Δσ = 1 MPa, let Δε 1j = Δε 0j (j = 1, 2), let σ zi = σ zi,min , give the initial value G0 = 10 10 of the target function, let G y = G0;

[0043] Then, in step (e), let σ z1 = σ z1 + k*Δσ; update the loop variables i, m, n;

[0044] Then, in step (f), let σ z2 = σ z2 + m*Δσ; update the loop variables i, n;

[0045] Then, in step (g), let σ z3 = σ z3 + n*Δσ; update the loop variable i;

[0046] Then, in step (h), the internal stress σ(z) and the strain ε ij of each material layer in the process section i are calculated.

[0047] Then, in step (i), the residual strain Δε' ij at the outlet of the process section i is calculated.

[0048] Then, in step (j), it is judged whether the inequality i < 3 is true. If the inequality is true, then let Δε = Δε' ij ij , i = i + 1, and go to step (h); if the inequality is not true, go to step (k);

[0049] Then, in step (k), the plate shape buckling amount control target function G(X) is calculated.

[0050] Then, in step (l), it is judged whether G(X) < G y is true. If the inequality is true, the tension control parameters and the plate shape buckling amount of the composite plate are recorded, let σ yi = σ zi , G y = G(X), and go to step (m); otherwise, go directly to step (m).

[0051] Then, in step (m), it is judged whether σ z3 < σ z3,max is true. If the inequality is true, let n = n + 1, and go to step (g); otherwise, go to step (n).

[0052] Then, in step (n), it is judged whether σ z2 < σ z2,max is true. If the inequality is true, let m = m + 1, and go to step (f); otherwise, go to step (o).

[0053] Then, in step (o), it is judged whether σ z1 < σ z1,max is true. If the inequality is true, let k = k + 1, and go to step (e); otherwise, go to step (p).

[0054] Finally, in step (p), the tension control parameters σ yi and the minimum plate shape buckling amount G y of the composite plate are outputted. The results are shown in Table 1, and the plate shape buckling amounts of the composite plate before and after optimization are shown in the attached figures. Figure 4

[0055] Table 1

[0056]

[0057]

[0058] Table 1 and the attached figures show that the tension control parameters and the minimum plate shape buckling amount of the composite plate are optimized. Figure 4 ​​As can be seen, after adopting the online control model for plate warpage described in this invention, compared with the production parameters set according to traditional experience, the maximum plate warpage decreased from 8.8288mm to 8.2738mm, and the plate shape control effect was good. It can be seen that the plate shape control model proposed in this invention can effectively control the plate warpage changes in the heat treatment process of stainless steel composite plates, optimize the plate shape state at the process exit, and has high production application value.

[0059] Example 2:

[0060] Refer to the instruction manual. Figure 5 Taking the stress-relief annealing heat treatment process of a 316L / Q235 composite board with specifications of 500×200×20mm at 950℃ as an example, the online control method for board warpage proposed in this invention is further illustrated, and its execution flow is shown in the attached figure. Figure 3 As shown:

[0061] In step (a), the basic equipment and process parameters of the heat treatment unit are collected. This mainly includes: the total number of heat treatment process sections (3), defining process section numbers {i, i = 1, 2, 3}; and collecting the maximum allowable tension σ within each process section. z1,max =10MPa, σ z2,max =8MPa, σ z3,max =12MPa; minimum value σ z1,min =0MPa, σ z2,min =0MPa, σ z3,min =0MPa, temperature at the end of process section 1 T1 = 950℃, temperature at the end of process section 2 T2 = 950℃, temperature at the end of process section 3 T3 = 25℃, T0 = 25℃.

[0062] Subsequently, in step (b), the parameters of the 316L / Q235 composite board are collected, mainly including: original length L = 500mm, total thickness h = 20mm, cladding thickness h1 = 5mm, base layer thickness h2 = 15mm, width b = 200mm, and thickness ratio λ = 0.25. The material layers j of the 316L / Q235 composite board are sequentially numbered 1 and 2 (1-316L cladding, 2-Q235 base layer), and the temperature of each process section is T. i Elastic modulus E of each material layer during elastic deformation stage ij Elastic modulus E′ during the strengthening stage ij Initial residual strain Δε of incoming material 0j linear expansion coefficient β ij Yield strength σ sij The initial value of the objective function for controlling the warpage of the composite panel is G0.

[0063] Subsequently, in step (c), relevant parameters are defined, mainly including: the internal stress σ(z) distributed along the thickness direction, and the total strain ε of each material layer.ij elastic strain ε eij residual strain at the inlet of the i-th process section Δε ij residual strain at the outlet of the i-th process section Δε' ij initial residual strain of the incoming material Δε 0j set tension of the i-th process section σ zi tension adjustment step Δσ; length of the clad plate L' during heat treatment, interlaminar bending moment M r distance between the strain neutral layer and the interface layer of the clad plate δ, corresponding central angle 2θ of the clad plate after bending, radius of curvature R, plate shape warping control objective function G(X), tension control parameter σ of the i-th process section yi optimal value of the plate shape warping of the clad plate G y tension adjustment parameters k, m, n

[0064] Subsequently, in step (d), the relevant parameters are assigned initial values: let i = 1, k = 0, m = 0, n = 0, set the tension adjustment step Δσ = 1 MPa, let Δε 1j = Δε 0j (j = 1, 2), let σ zi = σ zi,min , give the initial value of the objective function G0 = 10 10 , let G y = G0;

[0065] Subsequently, in step (e), let σ z1 = σ z1 + k * Δσ; update the loop variables i, m, n;

[0066] Subsequently, in step (f), let σ z2 = σ z2 + m * Δσ; update the loop variables i, n;

[0067] Subsequently, in step (g), let σ z3 = σ z3 + n * Δσ; update the loop variable i;

[0068] Subsequently, in step (h), calculate the stress σ(z) and strain ε ij in each material layer in the i-th process section;

[0069] Subsequently, in step (i), calculate the residual strain Δε' ij at the outlet of the i-th process section;

[0070] Subsequently, in step (j), determine whether the inequality i < 3 is true. If the inequality is true, let Δε ij = Δε' ij , i = i + 1, and go to step (h); if the inequality is not true, go to step (k);

[0071] Then, the plate shape warping amount control target function G(X) of the composite plate is calculated in step (k) ;

[0072] Then, it is judged whether G(X) < G y is established? If the inequality is not established, the tension control parameter and the plate shape warping amount of the composite plate are recorded, and let σ yi = σ zi , G y = G(X), and turn to step (m), otherwise, directly turn to step (m);

[0073] Then, it is judged whether σ z3 < σ z3,max is established? If the inequality is not established, let n = n + 1, and turn to step (g); otherwise, turn to step (n);

[0074] Then, it is judged whether σ z2 < σ z2,max is established? If the inequality is not established, let m = m + 1, and turn to step (f); otherwise, turn to step (o);

[0075] Then, it is judged whether σ z1 < σ z1,max is established? If the inequality is not established, let k = k + 1, and turn to step (e); otherwise, turn to step (p);

[0076] Finally, the tension control parameter σ yi of each process section and the minimum plate shape warping amount G y of the composite plate are output in step (p), and the results are shown in Table 1, and the plate shape warping amounts of the composite plate before and after optimization are shown in the attached Figure 4 .

[0077] Table 2

[0078]

[0079] It can be seen from Table 2 and the attached Figure 5 that the plate shape warping online control model can make the maximum plate shape warping amount decrease from 3.5801 mm to 3.2896 mm, and compared with the traditional experience method, the plate shape control model has good effect, can effectively control the plate shape warping change in the heat treatment process of the stainless steel composite plate, optimizes the plate shape state at the outlet of the process section, and has high production application value.

Claims

1. A method for online control of plate warpage during the heat treatment process of stainless steel / carbon steel composite plates, characterized in that: This includes the following steps performed by a computer: (a) Collect basic equipment and process parameters of the heat treatment unit, including: total number of heat treatment process sections (3), and define process section numbers { i , i =1, 2, 3}; Collect the maximum allowable tension value within each process section. Minimum value process section Temperature at the end Initial temperature of heat treatment ; (b) Collect parameters of the stainless steel / carbon steel composite plate, including: the original length of the stainless steel / carbon steel composite plate. L Total thickness h ,width b Thickness ratio λ For stainless steel / carbon steel composite plate material layers j Numbered sequentially as 1 and 2, where 1 represents the stainless steel cladding and 2 represents the carbon steel base layer; the thickness of each material layer... h j The temperature of each process section is Elastic modulus of each material layer during elastic deformation stage Elastic modulus during the strengthening stage Initial residual strain of incoming material coefficient of linear expansion Yield strength sij Initial value of the objective function for controlling the warpage of composite panels ; (c) Define relevant parameters, including: internal stress distributed along the thickness direction. Total strain of each material layer Elastic strain Residual strain at the inlet of the process section Process Section i Exit residual strain Initial residual strain of incoming material Tension settings for each process section Tension adjustment step size Length of composite plate during heat treatment Inter-story bending moment Distance between the strain neutral layer and the interface layer of the composite plate The central angle corresponding to the bending of the composite board radius of curvature R Plate warpage control objective function G( ) Tension control parameters for each process section Optimal value of composite panel warpage Tension adjustment parameters k, m, n; (d) Initialize relevant parameters: Let i =1, k=0, m=0, n=0, set the tension adjustment step size. , ( j =1, 2), let Given the initial value of the objective function ,make ; (e) Let Update the loop variable; (f) Let Update the loop variable; (g) Order Update the loop variable; (h) Calculate the internal stress of each material layer in process section i. ,strain ; (i) Calculation process segment i Exit residual strain ; (j) Determining Inequalities Whether it holds true or not, if the inequality holds true, then let , i=i+ 1. Proceed to step (h); if the inequality is not true, proceed to step (k); (k) Calculate the objective function for controlling the warpage of the composite panel. G( ) ; in: (l) Judgment G( )< Whether the inequality holds true or not, if the inequality does not hold true, then record the tension control parameters and the warping of the composite board, and let... , If yes, proceed to step (m); otherwise, proceed directly to step (m). (m) Judgment Whether the inequality holds true or not; if the inequality holds true, then let... If yes, proceed to step (g); otherwise, proceed to step (n). (n) judgment Whether the inequality holds true or not; if the inequality holds true, then let... If yes, proceed to step (f); otherwise, proceed to step (o). (o) Judgment Whether the inequality holds true or not; if the inequality holds true, then let... If yes, proceed to step (e); otherwise, proceed to step (p). (p) Output tension control parameters for each process section Minimum warpage of composite board .

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