JP7557324B2 - Design method for hot rolling of triple-layer clad plate and manufacturing method of triple-layer clad plate - Google Patents

Description

The present invention relates to a method for designing hot rolling of triple-layer clad plates and a method for manufacturing triple-layer clad plates.

Conventionally, clad metal plates in which multiple metal plates are joined together are known. As a method for manufacturing such clad plates, Patent Document 1 describes a method in which a base material, a cladding material, and a covering material are layered together to form a layered assembly material, which is hot-rolled, and then the covering material is removed. However, this method requires the additional work of separating the covering material after hot rolling. In addition, since there is a limit to the thickness that can be hot-rolled, there is a limit to the plate thickness of the base material, cladding material, and covering material, and ultimately productivity is low.

In Patent Document 2, when manufacturing two-layer clad material by hot rolling, the diameters of the upper and lower work rolls are made unequal, and the lubrication state between the work rolls and the material being rolled is adjusted to prevent warping. However, this method requires changing the work roll for each material characteristic, which reduces productivity. In addition, it is difficult to control the lubrication state stably, which ultimately reduces productivity.

Patent Document 3 describes a method for manufacturing clad steel plates using carbon steel as the base material and stainless steel as the clad material, in which warping is prevented by controlling the cooling conditions after rolling begins. However, with this method, cooling water is sprayed from above the conveyor table onto the material to be rolled, which is placed on the table, so the material to be rolled is pressed against the conveyor table, which may cause scratches on the surface and reduce the quality of the clad steel plate.

In Patent Document 4, in a hot rolling method for clad steel, which uses an iron alloy as the base material and copper or a copper alloy as the combined material, warping is prevented by rolling so that the rolling temperature and the transformation temperature of the iron alloy satisfy a specified formula. However, this method cannot be applied to clad materials with three or more layers. In addition, since it does not take into account the strain rate sensitivity coefficient, it is not an idea that can accurately reduce warping.

In Patent Document 5, the laminated material is sealed with a covering steel plate to form a covering steel plate assembly, which is then sandwiched between a steel base material and a warp prevention material, and the steel base material and the warp prevention material are welded together before hot rolling, and then the covering steel plate is removed to prevent warping. However, this method requires a lot of work to prepare before rolling and to remove the covering steel plate after rolling.

In Patent Document 6, a hot pressure control device for clad steel plate prevents warping by controlling the upper and lower rolls with different systems and rolling at different speeds. However, this device has the problem of being unable to fully control the configuration of clad material that causes large warping.

Patent Document 7 describes a method for manufacturing a three-layer clad aluminum alloy plate by specifying a small reduction rate at the beginning of rolling to eliminate poor bonding and to keep warpage to a minimum, thus avoiding the impossibility of manufacturing. However, this method has the problem that productivity decreases when the reduction rate is reduced.

Japanese Unexamined Patent Publication No. 61-232075 Japanese Unexamined Patent Publication No. 62-259607 Japanese Patent Application Publication No. 5-23702 Japanese Unexamined Patent Publication No. 59-56903 JP 62-158583 Publication Utility Model Publication No. 60-131213 Japanese Patent Application Publication No. 9-184038

The present invention was made in consideration of the above circumstances, and aims to provide a method for designing hot rolling of triple-layer clad plates and a method for manufacturing triple-layer clad plates that are highly productive and can reduce warping.

In order to solve the above problems, the present invention employs the following configuration.
[1] A method for designing hot rolling when manufacturing a three-layer clad plate by hot rolling a core material made of a metal plate, arranging a first skin material made of a metal plate different from the core material on one side of the core material, arranging a second skin material made of a metal plate different from the core material on the other side of the core material, and hot rolling the core material, wherein the core material, the first skin material, and the second skin material are each made of pure aluminum or an aluminum-based alloy,
The difference (CL 1 -CL 2 ) between a thickness ratio CL ₁ which is the ratio of the thickness of the first skin material to the total thickness CL _T of the core material, the first skin material, and the second skin material before the hot rolling, and a thickness ratio CL ₂ which is the ratio of the thickness of the _second skin material to the total thickness _{CL T} is defined as ΔCL;
When the deformation resistances of the core material, the first skin material, and the second skin material before the hot rolling at a strain rate of 0.1 sec ^-1 at the hot rolling temperature are respectively defined as s _c , s ₁ , and s ₂ , Δs and S are defined as the following formulas (1) and (2), respectively:
When the strain rate sensitivity coefficients of the deformation resistance at the hot rolling temperature of the core material, the first skin material, and the second skin material before the hot rolling are respectively _mc , _m1 , and _m2 , and Δm and M are defined as the following formula (3) and the following formula (4), respectively:
A design method for hot rolling of a three-layer clad plate, characterized in that, when S>0.65 and |ΔCL|>0.1, or when S≦0.65, the core material, the first skin material, and the second skin material are selected so as to satisfy the following formula (5).
Δs=(s ₁ - _{s 2} )/s _c (1)
S=0.5( _s1 + _s2 )/ _sc ...(2)
Δm= _m1 - _m2 ...(3)
M=0.5( _m1 + _m2 )/ _mc ...(4)
|k ₁ Δs+k ₂ Δm+k ₃ ΔCL|≦0.3...(5)

However, when S>0.65 and |ΔCL|>0.1, in the above formula (5), k ₁ =1.0, k ₂ =2.6, and k ₃ =−9.9+7.7S+1.5M;
When S≦0.65, k ₁ =−1.0, k ₂ =−0.7, and k ₃ =1.2−3.2S−4.3M in the above formula (5) , and the case where ΔCL=Δs=Δm=0 is excluded .
[2] The method for designing hot rolling of a three-layer clad plate according to [1] , wherein the core material is made of an Al-Mn aluminum-based alloy .
[3] The method for designing hot rolling of a three-layer clad plate according to [1] or [2] , wherein the first skin material is made of an Al-Si aluminum-based alloy .
[4] The method for designing hot rolling of a three-layer clad plate according to any one of [1] to [3] , wherein the second skin material is made of an Al-Zn based aluminum-based alloy .
[5] A method for manufacturing a three-layer clad plate, comprising: using the core material, the first skin material, and the second skin material selected in the design method for hot rolling of a three-layer clad plate described in any one of [1] to [4]; arranging the first skin material and the second skin material on one side and the other side of the core material, respectively; and hot rolling the core material.

In this specification, “k ₁ Δs+k ₂ Δm+k ₃ ΔCL” on the left side of the above formula (5) may be referred to as a parameter P.

The present invention provides a method for designing hot rolling of triple-layer clad plates and a method for manufacturing triple-layer clad plates that are highly productive and can reduce warping.

FIG. 1 is a model diagram showing a rolling analysis model by the finite element method when a core material, a first skin material, and a second skin material are hot-rolled to produce a three-layer clad plate. 2 is a graph showing the relationship between the Δs value and the curvature for Nos. 1 to 5, 6 to 9, 10 to 15, and 16 to 21 in Table 1. 3 is a graph showing the relationship between Δm value and curvature for Nos. 22 to 38 in Table 1. 4 is a graph showing the relationship between the ΔCL value and the curvature for Nos. 39 to 56 in Table 1. 5 is a graph showing the relationship between the parameter P and the predicted value of the curvature of the three-layer clad plate for Nos. 1 to 56 in Table 1, Nos. 57 to 60 in Table 4, and Nos. 61 to 82 in Table 5.

When a triple-layer clad plate is manufactured by placing a first skin material on one side of a core material and a second skin material on the other side of the core material and then hot rolling the plate, warping may occur. For example, if the first skin material and the second skin material are the same thickness and the deformation resistance of the first skin material is smaller than the deformation resistance of the second skin material, i.e., if the first skin material is easily stretched, the first skin material will elongate more than the second skin material during hot rolling, and the triple-layer clad plate after hot rolling will warp toward the second skin material.

For example, if the deformation resistance of the first skin material is the same as the deformation resistance of the second skin material and the thickness of the second skin material is greater than the thickness of the first skin material, assuming that the rolling reduction amounts for the first skin material and the second skin material are approximately the same, the elongation of the first skin material increases during hot rolling, and the three-layer clad plate after hot rolling warps toward the second skin material.

Therefore, in the past, when rolling a three-layer clad plate, the thicknesses and deformation resistances of the first and second skin materials placed on both sides of the core were made close to each other by ensuring symmetry of shape and material, and warping of the three-layer clad plate after hot rolling was prevented.

However, after extensive research, the inventors have found that the elongation of the skin material during hot rolling is affected not only by the deformation resistance and thickness, but also by the strain rate sensitivity coefficient of the deformation resistance at the hot rolling temperature. In other words, by focusing on the strain rate sensitivity coefficients of the first and second skin materials and selecting the first and second skin materials so as to optimize the combination of the strain rate sensitivity coefficients of the first and second skin materials, it has been found that it is possible to reduce the warpage of the triple-layer clad plate after hot rolling even when it is not possible to ensure the symmetry of the thickness and deformation resistance of the first and second skin materials arranged on both sides of the core material.

Furthermore, the inventors conducted an analysis using the finite element method and found that the warpage of the three-layer clad plate after hot rolling can be reduced when the absolute value of parameter P calculated from the relationship between the sheet thickness ratios CL ₁ , CL ₂ of the first skin material and the second skin material to the total thickness CL _T of the core material, the first skin material, and the second skin material before hot rolling, ΔCL (=CL ₁ -CL ₂ ), _the deformation resistances s _c , s ₁ , s ₂ of the core material, the first skin material, and the second skin material, and the strain rate sensitivity coefficients m c , m ₁ , m ₂ is 0.3 or less, more preferably 0.24 or less.

First, the inventors used the finite element method to predict the amount of warping in a triple-layer clad plate after hot rolling. Since it is empirically known that simulations reproduce reality well in plastic processing such as clad rolling, by examining a large number of conditions with a model material, they found conditions that result in small warping, as explained below.

FIG. 1 shows a rolling analysis model by the finite element method. The rolling analysis model was constructed in two dimensions, assuming a plane strain with an invariant sheet width. The shape of the finite element model was determined based on the thickness of each layer of the three-layer clad plate and the diameter of the rolling roll. The rolling roll was defined as a two-dimensional circle as a rigid body. That is, the total thickness of the three-layer clad plate before hot rolling (total thickness CL _T of the core material, first skin material, and second skin material before hot rolling) was set to 600 mm, and the diameter of the rolling roll was set to 850 mm both above and below. The length of the finite element model in the rolling direction was common to the core material, first skin material, and second skin material, and was set to 2.3 times or more of the total thickness (total thickness CL _T ). Regarding the element division in the longitudinal direction, the length per element in the longitudinal direction was common to the core material, first skin material, and second skin material, and was set to 1/20 or less of the roll radius. The coefficient of friction between the workpieces (core, first skin, and second skin) and the rolling rolls was set to 0.3 according to the Coulomb model.

The reduction ratio in the rolling analysis model was set to 6%. This is because it is empirically predicted that if warpage is small at a reduction ratio of 6%, rolling can be continued at a relatively large reduction ratio, allowing efficient production. Since the tendency of warpage does not change if the reduction ratio is 2-10%, when manufacturing the triple-layer clad plate according to the present invention by hot rolling, it is preferable to set the rolling ratio to 2-10%, as described below.

Regarding element division in the thickness direction, the length of each element in the thickness direction was set to 1/10 or less of the core thickness for the core material, and 1/4 or less of the thickness of each skin material for the first skin material and the second skin material. In this case, if the aspect ratio in the longitudinal direction/thickness direction was less than 1/2 or greater than 2, the elements were further divided so that the aspect ratio was between 1/2 and 2.

The interface between the core and the first skin, and the interface between the core and the second skin, were joined by sharing nodes of the finite elements.

As the physical property value of plastic deformation, the stress σ of each of the core material, the first skin material, and the second skin material was input using the following strain rate dependent formula (A). In formula (A), s is the deformation resistance at a strain rate _εv = 0.1, and m is the strain rate sensitivity coefficient. The deformation resistance s and the strain rate sensitivity coefficient m were measured based on the deformation resistance at a strain ε = 0.1 by performing a uniaxial tensile test or a uniaxial compression test with a variable strain rate.

σ=s( _εv /0.1) ^m ...(A)

As physical properties of elastic deformation, a Young's modulus of 40 GPa and a Poisson's ratio of 0.3 were used for aluminum and aluminum-based alloys. Since the Young's modulus and Poisson's ratio of aluminum alloys are less dependent on the alloy components, the above values were used as they are considered to be representative values around 400 to 500°C. It should be noted that the warping of clad metal plates is largely due to plastic deformation characteristics, and it has been confirmed that the elastic properties do not have much of an effect.

Similarly, for copper and copper-based alloys, a Young's modulus of 50 GPa and a Poisson's ratio of 0.35 were used. For titanium, a Young's modulus of 60 GPa and a Poisson's ratio of 0.35 were used.

Furthermore, after rolling analysis, 8 to 12 nodes in the center of the wall thickness were selected from the steady part of rolling, and the curvature (mm ^-1 ) was calculated from their coordinate values by the least squares method, and the warpage of the triple-layer clad plate was evaluated based on this curvature (mm ^-1 ).

The results of rolling analysis using the finite element method under the above conditions are shown in Table 1. Table 1 shows predicted values of the curvature (mm -1 ) of the clad plate after hot rolling under each condition (No. 1 to No. 56) in which the characteristic values of the core material, first skin material, and second skin material are changed when the core material, first skin material, and second skin material are stacked together and then hot rolled to produce a ^triple -layer clad plate. The characteristic values of the core material, first skin material, and second skin material that were changed were their respective deformation resistances s _c , s ₁ , s ₂ , strain rate sensitivity coefficients m _c , m ₁ , m ₂ , sheet thickness ratios CL ₁ , CL ₂ of the first skin material and second skin material, and the difference ΔCL (CL ₁ - CL ₂ ).

Δs, Δm, S, and parameter P in Table 1 were calculated from the following formulas (B) to (E). Parameter P in the table is the calculated value of " _k1 Δs+ _k2 Δm+ _k3 ΔCL" on the left side of the following formula (C). The present inventors found that the term on the right side of formula (C) (the absolute value of parameter P) correlates well with the amount of warpage after hot rolling.

From the results shown in Table 1, it was estimated that warpage of the triple-layer clad plate would be reduced under the conditions that S calculated by the following formula (B) is greater than 0.65 (S>0.65), the absolute value of ΔCL is greater than 0.1 (|ΔCL|>0.1), and the absolute value of the parameter P is 0.3 or less (satisfying the following formula (C)). It was also estimated that warpage of the triple-layer clad plate would be further reduced under the conditions that the absolute value of the parameter P is 0.24 or less.

Furthermore, from the results shown in Table 1, it was estimated that warping of the triple-layer clad plate would be reduced under conditions where S calculated by the following formula (B) is 0.65 or less (S≦0.65) and the absolute value of parameter P is 0.3 or less (satisfying the following formula (C)). It was also estimated that warping of the triple-layer clad plate would be further reduced under conditions where the absolute value of parameter P is 0.24 or less.

More specifically, in Table 1, the conditions for the example are those in which the parameter P is -0.30 or more and 0.30 or less, and the conditions for the comparative example are those in which the parameter P is less than -0.30 or more than 0.30. Under the conditions for the example, the predicted value of the curvature is in the range of -8.0 x 10 ^-5 (mm ^-1 ) to 8.0 x 10 ^-5 (mm ^-1 ). On the other hand, under the conditions for the comparative example, the curvature is in the range of less than -8.0 x 10 ^-5 (mm ^-1 ) or more than 8.0 x 10 ^-5 (mm ^-1 ). In this way, it was revealed that by adjusting the deformation resistances s _c , s ₁ , s ₂ of the core material, first skin material, and second skin material, the strain rate sensitivity coefficients m _c , m ₁ , m ₂ , the sheet thickness ratios CL ₁ , CL ₂ of the first skin material and second skin material, and the difference therebetween ΔCL (CL ₁ - CL ₂ ), so that the absolute value of the parameter P is 0.30 or less, it is possible to predict that the warpage of the three-layer clad plate after hot rolling can be reduced.

S=0.5( _s1 + _s2 )/ _sc ...(B)

|k ₁ Δs+k ₂ Δm+k ₃ ΔCL|≦0.3...(C)

Δs=(s ₁ −s ₂ )/s _c …(D)

Δm= _m1 - _m2 ...(E)

M=0.5( _m1 + _m2 )/ _mc ...(F)

Here, s _c , s ₁ , and s ₂ in the above formulas (B) and (D) are the deformation resistances at the hot rolling temperature at a strain rate of 0.1 sec ⁻¹ of the core material, the first skin material, and the second skin material, respectively.

In addition, Δs in the above formula (C) is calculated using the above formula (D), and Δm is calculated using the above formula (E). In addition, ΔCL in the above formula (C) is the difference between the thickness ratios _CL1 , _CL2 of the first skin material and the second skin material (ΔCL = _CL1 - _CL2 ). The thickness ratio _CL1 of the first skin material is the ratio of the thickness of the first skin material to the total thickness CL- _T of the core material, first skin material, and second skin material. In addition, the thickness ratio _CL2 of the second skin material is the ratio of the thickness of the second skin material to the total thickness CL- _T .

Moreover, the coefficients _k1 , _k2 , and _k3 in the above formula (C) are coefficients determined according to S and ΔCL. That is, when S>0.65 and |ΔCL|>0.1, _k1 =1.0, _k2 =2.6, and _k3 =-9.9+7.7S+1.5M. When S≦0.65, _k1 =-1.0, _k2 =-0.7, and _k3 =1.2-3.2S-4.3M. Here, M in the formula for determining the coefficient _k3 is determined by the above formula (F). These coefficients _k1 , _k2 , and _k3 are empirically determined.

In the above formulas (E) and (F), _m1 and _m2 are strain rate sensitivity coefficients of the deformation resistance of the first skin material and the second skin material at the hot rolling temperature, respectively, and are calculated from the above formula (A). Also, _mc in the above formula (F) is the strain rate sensitivity coefficient of the deformation resistance of the core material at the hot rolling temperature, and is calculated from the above formula (A).

The above formulas (B) to (F) and the method for determining the coefficients k ₁ , k ₂ and k ₃ will be described later.

The following describes a design method for hot rolling a triple-layer clad plate (hereinafter sometimes referred to as the "design method"), a manufacturing method for a triple-layer clad plate, and a triple-layer clad plate, which are embodiments of the present invention.

The design method of this embodiment has been made based on the above knowledge, and the core material, the first skin material, and the second skin material are selected so that the thicknesses, thickness ratios _CL1 , _CL2 , ΔCL, deformation resistances _sc , _s1 , _s2, and strain rate sensitivity coefficients _mc , _m1 , _m2 of the core material, the first skin material, and the second skin material before hot rolling each satisfy the condition of the above formula (C). In other words, in the hot rolling design method of this embodiment, when the thicknesses, thickness ratios _CL1 , _CL2 , ΔCL, deformation resistances _sc , _s1 , _s2 , and strain rate sensitivity coefficients _mc , _m1 , _m2 of the core material, first skin material, and second skin material before hot rolling satisfy the absolute value of the parameter P, which is the term on the left side of the above formula (C), of 0.3 or less, it is predicted that the warpage of the triple-layer clad plate after hot rolling will be small, and therefore hot rolling is judged to be possible. More preferably, the absolute value of the parameter P is 0.24 or less. If the absolute value of the parameter P is 0.24 or less, it is more preferable because it is predicted that the warpage of the triple-layer clad plate after hot rolling will be even smaller.

The core material, the first skin material, and the second skin material may each be pure aluminum or an aluminum-based alloy. Also, the core material, the first skin material, and the second skin material may each be pure copper or a copper-based alloy. Furthermore, the core material, the first skin material, and the second skin material may each be pure aluminum, an aluminum-based alloy, pure copper, a copper-based alloy, titanium, a titanium-based alloy, magnesium, or a magnesium-based alloy.

Next, characteristic values used in the design method of this embodiment will be described.
There are no particular limitations on the thickness of the core material, the first skin material, and the second skin material, but due to restrictions on hot rolling equipment, it is preferable that the total thickness _CLT of the core material, the first skin material, and the second skin material before hot rolling is, for example, 600 mm or less.

From the thicknesses of the core material, the first skin material, and the second skin material, a thickness ratio _CL1 is calculated, which is the ratio of the thickness of the first skin material to the total thickness CL _T. Similarly, a thickness ratio _CL2 is calculated, which is the ratio of the thickness of the second skin material to the total thickness CL _T. Furthermore, a difference ΔCL between the thickness ratio _CL1 and the thickness ratio _CL2 ( _CL1 - _CL2 ) is calculated.

In addition, deformation resistances s _c , s _{1 , and s 2 at the hot rolling temperature and a strain rate of 0.1 sec -1 of the core material, the first skin material, and the second skin material are determined, respectively. The method of determining the deformation resistances s c , s 1 , and s 2} ^will _{be described later} .

Furthermore, find S from the above formula (B) and Δs from the above formula (D).

The strain rate sensitivity coefficients _mc , _m1 , and _m2 of the deformation resistance at the hot rolling temperature of the core material, the first skin material, and the second skin material are determined from the above formula (A). A specific method for measuring the strain rate sensitivity coefficients _mc , _m1 , and _m2 will be described later.

Furthermore, Δm is calculated from the above formula (E), and M is calculated from the above formula (F).

Then, a parameter P is calculated as the calculated value of "k ₁ Δs + k ₂ Δm + k ₃ ΔCL" on the left side of the above formula (C) and determined. If the parameter P is in the range of -0.3 to 0.3 (if the above formula (C) is satisfied), it is estimated that warpage will be small when hot rolling is performed with the selected combination of core material, first skin material, and second skin material, and it is determined that rolling is possible, whereas if the parameter P is less than -0.3 or more than 0.3, it is estimated that warpage will be large when hot rolling is performed and it is determined that rolling is impossible.

In addition, in the design method of this embodiment, the case where S>0.65 and |ΔCL|>0.1 or the case where S≦0.65 is the prediction target, and the case where S>0.65 and |ΔCL|≦0.1 is not the prediction target of this embodiment.

The range of S>0.65 and |ΔCL|≦0.1, which is outside the scope of prediction in this embodiment, is one in which the asymmetry of the shape of the material before hot rolling is small to begin with, and hot rolling can be easily performed within this range, so there is little need to limit the absolute value of the parameter P. Therefore, the range of S>0.65 and |ΔCL|≦0.1 is outside the scope of this embodiment.

On the other hand, in the range of S > 0.65 and |ΔCL| > 0.1, the difference in the sheet thickness ratio between the first skin material and the second skin material becomes excessive, and the asymmetry of the shape of the material before hot rolling increases, which is expected to result in a large amount of warpage. Therefore, in the range of S > 0.65 and |ΔCL| > 0.1, it is necessary that the parameter P, which includes Δs, Δm, and ΔCL, be in the range of -0.3 to 0.3. If the parameter P is in the range of -0.3 to 0.3, the amount of warpage can be reduced even when the asymmetry of the shape of the material is large.

Furthermore, when S≦0.65, the deformation of the core material is small, and the deformation of the first skin material and the second skin material tends to concentrate, the asymmetry of the material before hot rolling becomes prominent, the amount of warping tends to increase, and rolling becomes difficult. Therefore, even when S≦0.65, it is necessary that the parameter P, which includes Δs, Δm, and ΔCL, is in the range of -0.3 to 0.3. If the parameter P is in the range of -0.3 to 0.3, the amount of warping can be reduced even when the material shape is highly asymmetry.

Next, a method for measuring the deformation resistances s _c , s ₁ , and s ₂ of the core material, the first skin material, and the second skin material at the hot rolling temperature at a strain rate of 0.1 sec ^-1 will be described. Also, a method for measuring the strain rate sensitivity coefficients m _c , m ₁ , and m ₂ of the deformation resistances of the core material, the first skin material, and the second skin material at the hot rolling temperature will be described.

The test pieces are cylindrically cut out from near the center of the thickness and width of the core material, the first skin material, and the second skin material. The cylinder is cut so that its axial direction coincides with the thickness direction of the material to be rolled. The dimensions of the test piece are 8 mm in diameter and 12 mm in height.

The test piece is heated to the test temperature at a rate of 60°C/min or more, and is held at that temperature for 2 to 6 minutes after reaching the test temperature, and then compressed. The test temperature can be selected from the temperature at which the material being examined will be hot-rolled. For example, for aluminum, the range is 300 to 600°C. Just before compression, the test piece is allowed to run 0.5 mm free (run-up), and during compression, strain is applied to the test piece at a constant strain rate. At this time, the strain is logarithmic (true) strain.

The amount of compression L ^sample,end is measured from the change in specimen height before and after compression.

During compression, the load F and the displacement L are ^measured . The point at which the load rises from the free running (approach) is set as the zero point of the displacement.

The displacement ^Lmeasure measured during compression includes the effect of deformation of each part of the device due to the load, so the displacement amount ^Lmeasure,end at the moment of the end of compression does not completely match the compression amount ^Lsample,end . This means that the displacement ^Lmeasure needs to be corrected. For this reason, the displacement ^Lmeasure is linearly corrected by ^Lcorrect = (Lsample ^,end / ^Lmeasure,end ) x ^Lmeasure .

The strain ε=|ln((H ^initial −L ^correct )/H ^initial )| is calculated from the corrected displacement L ^correct and the original height H ^initial of the test piece.

The stress is calculated by dividing the test load by the cross-sectional area during compression. Assuming a constant volume, the cross-sectional area during compression is calculated as A = (H ^initial / (H ^initial - L ^correct )) x A ^initial , where A ^initial is the cross-sectional area of the cylindrical test piece before compression.

The deformation resistance σ is obtained when the strain ε = 0.1.

Such evaluation is carried out at strain rates ε _v of 0.01 sec ⁻¹ , 0.1 sec ⁻¹ , and 1 sec ⁻¹ for n=2 or more, and the average value of the results at a strain rate of 0.1 sec ⁻¹ is defined as s (s _c , s ₁ , s ₂ ).

Moreover, the above results are fitted to the equation σ=s(ε _v /0.1) ^m by the least squares method to obtain the strain rate sensitivity coefficient m(m _c , m ₁ , m ₂ ).

Next, a method for manufacturing the three-layer clad plate of this embodiment will be described.
In the manufacturing method of a three-layer clad plate of this embodiment, the core material, first skin material, and second skin material selected in the above design method are used, the first skin material and the second skin material are placed on one side and the other side of the core material, respectively, and the three-layer clad plate is manufactured by hot rolling.

The heating temperature before hot rolling is, for example, in the range of 300 to 600°C when the core material, first skin material, and second skin material are each pure aluminum or an aluminum-based alloy. Also, when the core material, first skin material, and second skin material are each pure copper or a copper-based alloy, the heating temperature is, for example, in the range of 400 to 1000°C. Furthermore, when the core material, first skin material, and second skin material are titanium or a titanium-based alloy, the heating temperature is in the range of 600 to 1000°C. Furthermore, when the core material, first skin material, and second skin material are magnesium or a magnesium-based alloy, the heating temperature is in the range of 300 to 500°C.

Furthermore, when the core material, first skin material, and second skin material are made of different materials, for example, when combining aluminum and copper, it is preferable to take into account the recrystallization temperature and melting point of each metal and adjust the heating temperature for hot rolling to be within the range of the recrystallization temperature or higher and lower than the melting point of each metal.

The reduction rate of the hot rolling may be 2% or more, or 4% or more. If the reduction rate is 2% or more, the bonding strength of the core material, the first skin material, and the second skin material can be made sufficient, and if it is 4% or more, the manufacturing efficiency can be further improved. There is no need to limit the upper limit of the reduction rate. In addition, if the reduction rate is within a certain range, the increase in the amount of warping tends to be suppressed, so it may be, for example, 30% or less, 20% or less, or 10% or less.

The triple-layer clad plate manufactured by hot rolling is made of the core material, the first skin material, and the second skin material selected by the above design method. This triple-layer clad metal plate has a curvature in the range of -8.00 x 10 ^-5 mm ^-1 to 8.00 x 10 ^-5 mm ^-1 .

Next, the reason for deriving the above formula (C) used in the determination method of this embodiment will be described.
In the rolling analysis by the finite element method described above, as shown in Nos. 1 to 56 in Table 1, model materials assuming predetermined material properties were used to evaluate the effects of the properties and the cladding ratio.

FIG. 2 is a graph showing the relationship between the Δs value and the curvature for Nos. 1 to 5, 6 to 9, 10 to 15, and 16 to 21.
The influence of the Δs value in formula (D) can be confirmed in conditions No. 1 to 21. In Table 1 and FIG. 2, conditions No. 1 to 21 are divided by the range of S value, No. 1 to 9 are conditions where S>0.65, and No. 10 to 21 are conditions where S≦0.65. In addition, when No. 1 to 5, No. 6 to 9, No. 10 to 15, and No. 16 to 21 are each grouped, only Δs is varied within each group. Note that s ₁ , s ₂ , and s _c are physical quantities with units (MPa), so they are divided by s _c to make them more general (formula (D)). The S value is an average evaluation value that determines whether the bark material is softer than the core material (formula (B)).

As shown in Figure 2, it can be seen that there is a nearly linear correlation between the Δs value and warpage. For Nos. 1 to 9 (S > 0.65), there is a positive correlation and the slope is roughly constant. This can be interpreted as meaning that the harder material does not stretch during rolling, but is pulled and warps instead. Additionally, for Nos. 10 to 21 (S ≦ 0.65), there is a negative correlation and the slope is roughly constant. This is thought to be due to the fact that the skin material is soft, causing strain to concentrate only on the surface, which is the opposite of the trend for Nos. 1 to 9.

Next, Fig. 3 shows a graph of the relationship between the Δm value and the curvature for Nos. 22 to 38.
As shown in Figure 3, the effect of Δm can be confirmed in Nos. 22 to 38. In Table 1 and Figure 3, Nos. 22 to 38 are classified by S value, with Nos. 22 to 30 having S>0.65 and Nos. 31 to 38 having S≦0.65. In addition, when Nos. 22 to 25, 26 to 30, 31 to 34, and 35 to 38 are each grouped, only Δm is varied within each group. Note that _m1 , _m2 , and _mc are dimensionless numbers with no unit, so division by _mc is not performed.

As shown in Figure 3, Δm and warpage show a nearly linear correlation. In Nos. 22-30 (S>0.65), Δm and warpage are positively correlated, and the slope is roughly constant. It can be interpreted that the larger _m1 and _m2 are, the harder the material is to stretch by rolling due to hardening caused by strain, and the material is pulled and warped. Nos. 31-38 (S≦0.65) have a small negative slope. This is thought to be due to the influence of strain being concentrated only on the surface due to the softness of the skin material, which is the opposite of the trend in Nos. 22-30.

Next, Fig. 4 shows a graph of the relationship between the ΔCL value and the curvature for Nos. 39 to 56.
As shown in Figure 4, the effect of ΔCL can be confirmed in Nos. 39 to 56. In Table 1 and Figure 4, Nos. 39 to 56 are classified by S value, with Nos. 39 to 48 having S>0.65 and Nos. 49 to 56 having S≦0.65. In addition, when Nos. 39 to 43, Nos. 44 to 48, Nos. 49 to 52, and Nos. 53 to 56 are each grouped, only ΔCL is varied within each group.

As shown in Figure 4, there is a nearly linear correlation between ΔCL and warpage. It is suggested that the slope varies depending on the physical properties of the core and skin materials. When the S value is large, of the first and second skin materials, the skin material with the larger sheet thickness is not fully strained, while the skin material with the smaller sheet thickness tends to be uniformly strained from rolling, resulting in warping on the side that is not fully strained. The extent of this phenomenon varies depending on the strength of the material. Note that ΔCL is only considered in the negative range because this is sufficient from the standpoint of symmetry, and ΔCL is not limited to being negative.

Based on the above trends, we decided to express the warping using the following parameter P.

P=k ₁ Δs+k ₂ Δm+k ₃ ΔCL

The coefficient _k1 of Δs and the coefficient _k2 of Δm in the above formula correspond to the slope of the straight line shown in Figures 2 and 3. From the above considerations, it was thought that _k1 and _k2 could be constants. On the other hand, the coefficient _k3 of ΔCL depends on the physical properties as shown in Figure 4. Since Δs and Δm have already been used, it was considered to express the coefficient _k3 with S and M. As a result of careful consideration based on the results of No. 1 to No. 56, it was found that the parameter P and the warpage (curvature) of the simulation are well correlated by setting the coefficients as follows.

When S>0.65, k ₁ =1.0, k ₂ =2.6, k ₃ =-9.9+7.7S+1.5M

When S≦0.65, k ₁ =−1.0, k ₂ =−0.7, and k ₃ =1.2−3.2S−4.3M

5 shows the relationship between the parameter P and the warpage (curvature). It was found that it is possible to predict that when the parameter P is in the range of -0.3 to 0.3, the curvature will be in the range of -8.00×10 ^-5 mm ^-1 to 8.00×10 ^-5 mm ^-1 .

It was also found that when the parameter P is in the range of −0.24 to 0.24, it can be estimated that the curvature is in the range of −5.50×10 ⁻⁵ mm ⁻¹ to 5.50×10 ⁻⁵ mm ⁻¹ .
The details of FIG. 5 will be described later.

As described above, according to the design method of this embodiment, by focusing on the strain rate sensitivity coefficients of the first skin material and the second skin material and selecting the first skin material and the second skin material so as to optimize the combination of the strain rate sensitivity coefficients of the first skin material and the second skin material, it can be inferred that the warpage of the triple-layer clad plate after hot rolling can be reduced even when the symmetry of the thickness and deformation resistance of the first skin material and the second skin material arranged on both sides of the core material cannot be ensured. This makes it possible to easily design the combination of the core material, the first skin material, and the second skin material that constitute the triple-layer clad metal plate, and to increase the productivity of the triple-layer clad metal plate.
Furthermore, according to the method for manufacturing a three-layer clad metal plate of this embodiment, a three-layer clad metal plate with a small amount of warping can be manufactured.

The present invention will now be described in more detail with reference to examples.
The materials shown in the following Tables 2 and 3 were prepared. Tables 2 and 3 show the material type of each material, the deformation resistance s (MPa) at 440°C, 480°C, and 520°C, and the measured values of the strain rate sensitivity coefficient m.

The materials shown in Table 2 were hot rolled to adjust the plate thickness to obtain the core, first skin, and second skin for clad rolling. The first skin and second skin were then placed on one side and the other side of the core, respectively, and this laminate was hot rolled. The heating temperature of the laminate before hot rolling was 480°C. The roll diameter of the rolling roll during hot rolling was 860 mm. The reduction ratio of the hot rolling was in the range of 4 to 10%. In this way, three-layer clad plates No. 57 to 60 shown in Table 4 were manufactured. The obtained three-layer clad plates were evaluated for warping and manufacturability. The results are shown in the lower part of Table 4.

The material type, casting method, and homogenization temperature for the materials shown in Table 2 are shown below. The "%" in the chemical composition is mass %. Also, "hot rolling" listed in AA1 to AA3 and AC1 to AC5 means that blooming and hot rolling were performed to obtain the specified plate thickness.

"AA1" Al-Si brazing material AA1. Melted and cast. Homogenized heat treatment 550°C. Hot rolled.
"AA2" Al-Si brazing material AA2. Melted and cast. Homogenized heat treatment 450°C. Hot rolled.
"AA3" Al-Si brazing material AA3. Melted and cast. Homogenized heat treatment 500°C. Hot rolled.
"AB1" Al-Mn core material AB1. Melted and cast. Homogenized heat treatment at 500°C.
"AB2" Al-Mn core material AB2. Melted and cast. Homogenized heat treatment at 600°C.
"AC1" Al-Zn sacrificial material AC1. Melted and cast. Homogenized heat treatment 550°C. Hot rolled.
"AC2" Al-Zn sacrificial material AC2. Melted and cast. Homogenized heat treatment 450°C. Hot rolled.
"AC3" Al-Zn sacrificial material AC3. Melted and cast. Homogenized heat treatment 550°C. Hot rolled.
"AC4" Al-Zn sacrificial material AC4. Melted and cast. Homogenized heat treatment 450°C. Hot rolled.
"AC5" Al-Zn sacrificial material AC5. Melted and cast. Homogenized heat treatment 500°C. Hot rolled.

The rolling conditions for Nos. 57 to 60 are as follows:
"Rolling of No. 57" Total thickness of laminate before rolling CL _T : 510 mm. After bonding, roll with a reduction of 4 to 10% for thicknesses of 400 mm or more, and over 10% for thicknesses less than 400 mm. Almost no warping, good manufacturability.
"Rolling of No. 58" Total thickness of laminate before rolling CL _T : 510 mm. After bonding, roll with a reduction of 4 to 10% for thicknesses of 350 mm or more, and over 10% for thicknesses of less than 350 mm. Large upward warping and poor manufacturability.
"Rolling of No. 59" Total thickness of laminate before rolling CL _T : 590 mm. After bonding, roll with a reduction of 4 to 10% for thicknesses of 400 mm or more, and over 10% for thicknesses of less than 400 mm. Good manufacturability with slight upward warping.
"Rolling of No. 60" Total thickness of laminate before rolling CL _T : 510 mm. After bonding, roll reduction is 4-10% for thicknesses of 350 mm or more, and over 10% for thicknesses of less than 350 mm. Large upward warping, poor manufacturability. Rolls are often stopped and returned during rolling.

As a determination method according to the present invention, _CL1 , _CL2 , Δs, Δm, ΔCL, S, and parameter P were determined from the deformation resistance (MPa), strain rate sensitivity coefficient, and sheet thickness at 480°C of the materials shown in Table 2. These are also shown in Table 4. Δs, Δm, ΔCL, S, and parameter P were determined by the above formulas (B) to (F). The results are shown in the upper part of Table 4. The curvatures shown in the upper part of Table 4 are predicted values determined by the finite element method.

As shown in Table 4, the results of the determination method according to the present invention show a good agreement with the warpage of the three-layer clad metal plate actually manufactured.

That is, No. 57 has a parameter P of -0.079, which is within the range of -0.3 to 0.3, and the predicted value of the curvature obtained by the finite element method is -1.66 x 10 ^-5 (/mm), which is within the range of -8.00 x 10 ^-5 mm ^-1 to 8.00 x 10 ^-5 mm ^-1 . And, the actual manufacturing result is evaluated as having almost no warpage. The same is true for No. 59.

On the other hand, No. 58 has a parameter P of 0.387, which is outside the range of -0.3 to 0.3, and the predicted value of the curvature obtained by the finite element method is 8.77×10 ^-5 (/mm), which is outside the range of -8.00×10 ^-5 mm ^-1 to 8.00×10 ^-5 mm ^-1 . And the actual manufacturing result is evaluated as having a large upward warpage. The same is true for No. 60.

From these results, it is clear that the results of the determination method according to the present invention are in good agreement with the amount of warping of the three-layer clad metal plate actually manufactured. Therefore, it is clear that the determination method according to the present invention has very high prediction accuracy.

In addition, in Table 5, _CL1 , _CL2 , Δs, Δm, ΔCL, S, and parameter P were calculated from the deformation resistance (MPa), strain rate sensitivity coefficient, and plate thickness of the materials shown in Tables 2 and 3. These are shown in Table 5. Δs, Δm, ΔCL, S, and parameter P were calculated using the above formulas (B) to (F). In addition, the curvatures shown in Table 5 are predicted values of curvatures calculated using the finite element method.

As shown in Table 5, it is possible to accurately predict the amount of warping of a three-layer clad plate after hot rolling, even when the material is an aluminum alloy, a Cu alloy, or a Ti alloy.

Figure 5 also shows the relationship between the parameter P and the curvature in Tables 1, 4, and 5. The curvatures shown in Figure 5 are predicted values of curvature obtained by the finite element method. As shown in Figure 5, even if the core material, first skin material, and second skin material are aluminum-based alloy, pure copper, copper-based alloy, and titanium, respectively, it can be seen that there is a correlation between the parameter P and the curvature. This demonstrates that the determination method of the present invention can accurately predict the curvature of a three-layer clad plate after hot rolling using the parameter P.

Claims (5)

A method for designing the hot rolling in a case where a three-layer clad plate is manufactured by hot rolling a core material made of a metal plate, a first skin material made of a metal plate different from the core material is arranged on one side of the core material, a second skin material made of a metal plate different from the core material is arranged on the other side of the core material, and the three-layer clad plate is manufactured by hot rolling,
the core material, the first skin material, and the second skin material are each made of pure aluminum or an aluminum-based alloy,
The difference (CL 1 -CL 2 ) between a thickness ratio CL ₁ which is the ratio of the thickness of the first skin material to the total thickness CL _T of the core material, the first skin material, and the second skin material before the hot rolling, and a thickness ratio CL ₂ which is the ratio of the thickness of the _second skin material to the total thickness _{CL T} is defined as ΔCL;
When the deformation resistances of the core material, the first skin material, and the second skin material before the hot rolling at a strain rate of 0.1 sec ^-1 at the hot rolling temperature are respectively defined as s _c , s ₁ , and s ₂ , Δs and S are defined as the following formulas (1) and (2), respectively:
When the strain rate sensitivity coefficients of the deformation resistance at the hot rolling temperature of the core material, the first skin material, and the second skin material before the hot rolling are respectively _mc , _m1 , and _m2 , and Δm and M are defined as the following formula (3) and the following formula (4), respectively:
A design method for hot rolling of a three-layer clad plate, characterized in that, when S>0.65 and |ΔCL|>0.1, or when S≦0.65, the core material, the first skin material, and the second skin material are selected so as to satisfy the following formula (5).
Δs=(s ₁ - _{s 2} )/s _c (1)
S=0.5( _s1 + _s2 )/ _sc ...(2)
Δm= _m1 - _m2 ...(3)
M=0.5( _m1 + _m2 )/ _mc ...(4)
|k ₁ Δs+k ₂ Δm+k ₃ ΔCL|≦0.3...(5)
However, when S>0.65 and |ΔCL|>0.1, in the above formula (5), k ₁ =1.0, k ₂ =2.6, and k ₃ =−9.9+7.7S+1.5M;
When S≦0.65, k ₁ =−1.0, k ₂ =−0.7, and k ₃ =1.2−3.2S−4.3M in the above formula (5) , and the case where ΔCL=Δs=Δm=0 is excluded . The method for designing a hot-rolled triple-layer clad plate according to claim 1, characterized in that the core material is made of an Al-Mn based aluminum-based alloy . The method for designing hot rolling of a three-layer clad plate according to claim 1 or 2, characterized in that the first skin material is formed from an Al-Si aluminum-based alloy . The method for designing hot rolling of a three-layer clad plate according to any one of claims 1 to 3, characterized in that the second skin material is formed from an Al-Zn based aluminum-based alloy . A method for manufacturing a three-layer clad plate, comprising: using the core material, the first skin material, and the second skin material selected in the design method for hot rolling of a three-layer clad plate described in any one of claims 1 to 4; arranging the first skin material and the second skin material on one side and the other side of the core material, respectively; and hot rolling the core material.

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