Cladding material made of aluminum alloy

Abstract

To provide a cladding material.SOLUTION: Provided is a cladding material in which the cladding ratio of a core material is 71% or more and 97% or less, the core material contains Mn, Si, Fe, Cu, Mg, and the balance consists of Al and inevitable impurities. In a cross section of the core material before brazing heat treatment which is severally parallel with a rolling direction and a lateral direction, the density of an intermetallic compound having the average particle diameter more than 50 nm and 100 nm or less is 0.5×106 pcs. / mm2 or more and 6.0×106 pcs. / mm2 or less, the density of an intermetallic compound having the average particle diameter more than 100 nm and 300 nm or less is 1.0×106 pcs. / mm2 or more and 5.0×106 pcs. / mm2 or less, and the density of an intermetallic compound having the average particle diameter more than 500 nm and 1500 nm or less is 5.0×103 pcs. / mm2 or more and 15.0×103 pcs. / mm2 or less. In the core material before brazing heat treatment, when the solid solubility of Mn is a mass%, the solid solubility of Si is b mass%, the solid solubility of Cu is c mass%, the solid solubility of Mg is d mass%, and 11a+2b+6c+9d is a solid solubility evaluation value, a solid solubility evaluation value is less than 9.0 mass%.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a clad material made of an aluminum alloy. [Background technology]

[0002] Automotive heat exchangers are becoming lighter in order to improve fuel efficiency and save space. To achieve this, the components used, such as single-sided brazing clad brazing sheets, are required to be thinner and stronger.

[0003] In the brazing sheet disclosed in Patent Document 1, if the intermetallic compounds having a size of 0.2 μm to 0.5 μm contained in the core material have an area fraction of 5% or less in any cross section of the core material before brazing heat treatment, it is possible to obtain a Mn solid solution amount of 0.2% or more after brazing, which provides a sufficient solid solution strengthening effect and provides sufficient strength after brazing heat treatment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5793336 Paragraph (0047) Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the increasing demand for CO2 reduction has led to a demand for the use of scrap materials, which tends to increase the types and amounts of elements contained. While this contributes to increasing the strength of the material, it also hinders the formability of heat exchangers, which tend to have increasingly complex shapes. The core material in Patent Document 1 is made of an aluminum alloy containing multiple elements such as Mn, Si, and Cu, but it does not solve the formability issues of aluminum alloys containing these multiple elements. It is desirable to solve this issue not only for brazing sheets, but also for clad materials with various clad configurations.

[0006] In view of the above problems, an object of the present invention is to provide a clad material made of an aluminum alloy. [Means for solving the problem]

[0007] The present invention provides an aluminum alloy clad material in which a skin material consisting of at least one of a brazing material and a sacrificial material is clad on one or both sides of a core material, the cladding ratio of the core material being 71% to 97%, and the core material containing 0.8% to 1.8% by mass of Mn, 0.05% to 1.5% by mass of Si, 0.05% to 0.5% by mass of Fe, 0.05% to 1.5% by mass of Cu, and 0.001% to 1.0% by mass of Mg, with the balance being Al and unavoidable impurities. In a cross section of the core material before brazing heat treatment, which is parallel to the rolling direction and the transverse direction perpendicular to both the rolling direction and the thickness direction, the number of intermetallic compounds having an average grain size of more than 50 nm and 100 nm is 0.5 × 10 6 pieces / mm 2 Over 6.0 x 10 6 pieces / mm 2 or less, and the number of intermetallic compounds with an average particle size of more than 100 nm and 300 nm or less is 1.0 × 10 6 pieces / mm 2 Over 5.0 x 10 6 pieces / mm 2 The number of intermetallic compounds having an average particle size of more than 500 nm and less than 1500 nm is 5.0 × 10 3 pieces / mm 2 Over 15.0 x 10 3 pieces / mm 2 Furthermore, in the core material before the brazing heat treatment, if the solid solubility of Mn is a%, the solid solubility of Si is b%, the solid solubility of Cu is c%, and the solid solubility of Mg is d%, and further the solid solubility evaluation value is 11a + 2b + 6c + 9d, the solid solubility evaluation value is less than 9.0% by mass.

[0008] Core cladding ratio: 71% to 97% In clad materials, the cladding ratio of the core material is set to 71% or more and 97% or less, which is much higher than the cladding ratio of the skin material. Furthermore, the skin material has superior formability for deforming compared to the core material. Therefore, the formability and strength of the entire clad material are largely determined by the formability and strength of the core material. If the core material's cladding ratio is less than 71%, the skin material contributes to formability and strength, while if the core material's cladding ratio exceeds 97%, manufacturing becomes difficult and undesirable. Therefore, in the present invention, the core material's composition and metal structure (solid solubility and distribution of intermetallic compounds) are controlled to improve the formability and strength of the core material.

[0009] [Heartwood components] Mn: 0.8% by mass or more and 1.8% by mass or less The inclusion of Mn in the core improves the strength of the material through solid solution strengthening and the precipitation of intermetallic compounds such as Al-Mn, Al-Mn-Si, Al-Mn-Fe, and Al-Mn-Fe-Si. If the Mn content is less than 0.8% by mass, the desired strength improvement effect cannot be obtained. On the other hand, if the Mn content exceeds 1.8% by mass, large intermetallic compounds are formed during casting, reducing manufacturability.

[0010] Si: 0.05 mass% or more and 1.5 mass% or less The core material contains Si, which improves its strength through solid solution strengthening and dispersion strengthening caused by the precipitation of intermetallic compounds such as Al-Mn-Si and Al-Mn-Fe-Si. If the Si content is less than 0.05% by mass, the desired strength improvement effect cannot be obtained. On the other hand, if the Si content exceeds 1.5% by mass, the melting point decreases.

[0011] Fe: 0.05 mass% or more and 0.5 mass% or less The inclusion of Fe in the core material improves the strength of the material by precipitating intermetallic compounds, primarily Al-Fe, Al-Fe-Si, Al-Mn-Fe, and Al-Mn-Fe-Si. Because Fe exists as an impurity in the raw material, a Fe content of less than 0.05% by mass is costly and does not achieve the desired strength improvement effect. On the other hand, if the Fe content exceeds 0.5% by mass, large intermetallic compounds are formed during casting, reducing manufacturability.

[0012] Cu: 0.05 mass% or more and 1.5 mass% or less The core material contains Cu, which improves the material strength through solid solution strengthening. If the Cu content is less than 0.05% by mass, the desired strength improvement effect cannot be obtained. On the other hand, if the Cu content exceeds 1.5% by mass, cracks are likely to occur during casting.

[0013] Mg: 0.001 mass% or more and 1.0 mass% or less The core material contains Mg, which improves the strength of the material by providing solid solution strengthening and precipitation as an Mg-Si intermetallic compound through aging precipitation. If the Mg content is less than 0.001% by mass, the desired strength improvement effect cannot be obtained. On the other hand, if the Mg content exceeds 1.0% by mass, cracks are likely to occur during hot rolling, reducing manufacturability.

[0014] [Metal structure of core wood] 1. Distribution of intermetallic compounds The distribution state of the intermetallic compounds affects the formability of the clad material, which is used to deform it into a desired shape before brazing heat treatment, and the strength of the clad material after brazing heat treatment. However, since the size (particle size) of the intermetallic compounds that affect the formability and strength varies, it is necessary to carefully adjust the distribution state (number) for each particle size.

[0015] 1-1. Intermetallic compounds with an average particle size of more than 50 nm and less than 100 nm The number of intermetallic compounds with an average particle size of more than 50 nm and less than 100 nm is 0.5 × 10 6 pieces / mm 2 Over 6.0 x 10 6 pieces / mm 2 These intermetallic compounds interact with dislocations introduced during deformation, improving work hardening capacity and thereby improving formability. 6 pieces / mm 2 If it is less than 6.0 x 10 6 pieces / mm 2 If the number of dislocations exceeds 100, the distribution of dislocations becomes non-uniform and formability deteriorates.

[0016] 1-2. Intermetallic compounds with an average particle size of more than 100 nm and less than 300 nm If fine intermetallic compounds are dispersed in the core material after brazing heat treatment, the strength of the core material after brazing heat treatment improves. However, the finer the intermetallic compounds dispersed before brazing heat treatment, the more likely they are to redissolve during brazing heat treatment. Therefore, in order to leave fine intermetallic compounds after brazing heat treatment and exert strengthening, it is necessary to disperse intermetallic compounds of an appropriate size in the core material before brazing heat treatment. When the average particle size of the intermetallic compounds is more than 100 nm and less than 300 nm, they are less likely to redissolve during brazing heat treatment and can maintain a fine state, which contributes to improving the strength of the core material after brazing heat treatment. The number of intermetallic compounds with an average particle size of more than 100 nm and less than 300 nm is 1.0 x 10 6 pieces / mm 2 Over 5.0 x 10 6 pieces / mm 2 The number is 1.0×10 6 pieces / mm 2 If it is less than 5.0 x 10 6 pieces / mm 2 Above this, the effect saturates.

[0017] 1-3. Intermetallic compounds with an average particle size of more than 500 nm and less than 1500 nm During the manufacturing of clad materials, strain concentrates around coarse intermetallic compounds with an average grain size exceeding 1500 nm. Even if the average grain size is an appropriate size of 1500 nm or less, if it is distributed loosely, strain will become localized. These strains cause non-uniform deformation of the clad material, resulting in reduced formability. On the other hand, if intermetallic compounds with an average grain size exceeding 500 nm and less than 1500 nm are dispersed appropriately, strain concentration will be averaged out, resulting in uniform deformation. The number of intermetallic compounds with an average grain size exceeding 500 nm and less than 1500 nm is 5.0 x 10 3 pieces / mm 2 Over 15.0 x 10 3 pieces / mm 2 The number is 5.0 × 10 3 pieces / mm 2 If it is less than 15.0 x 10 3 pieces / mm 2If the temperature exceeds this value, the intermetallic compounds become densely dispersed, which promotes the destruction of the clad material.

[0018] 2.Solid solubility of Mn, Si, Cu and Mg before brazing heat treatment The presence of solute elements interacts with dislocations introduced during deformation of the clad material, resulting in uneven distribution of dislocations, which reduces the formability of the clad material when it is deformed into a desired shape. Furthermore, the strength of the interaction between solute elements and dislocations varies depending on the type of solute element. When many types of solute elements are present, it is necessary to comprehensively adjust the influence of the interaction between each element and dislocation.

[0019] In the core material before brazing heat treatment, the solid solubility of Mn is a mass%, the solid solubility of Si is b mass%, the solid solubility of Cu is c mass%, and the solid solubility of Mg is d mass%, and the solid solubility evaluation value is 11a + 2b + 6c + 9d. This solid solubility evaluation value is a parameter that indicates the degree of influence of the interaction between each element (Mn, Si, Cu, and Mg) and dislocations. The solid solubility evaluation value of the core material of the clad material before brazing heat treatment is adjusted to be less than 9.0 mass% (satisfying the relationship 11a + 2b + 6c + 9d < 9.0). A solid solubility evaluation value of less than 9.0 mass% improves the formability of the clad material. A solid solubility evaluation value of 9.0 mass% or more results in a high overall content of multiple solid solution elements, reducing the formability of the clad material. The solid solubilities a, b, c, and d of each element (Mn, Si, Cu, and Mg) can be determined by inductively coupled plasma atomic emission spectroscopy of the solution obtained by dissolving at least a portion of the core material before brazing heat treatment in hot phenol and filtering the intermetallic compounds (crystallized particles, precipitates, etc.) that are not dissolved in hot phenol and are contained in the solution.

[0020] The core material may further contain at least one element selected from the group consisting of Ti, Zr, Cr, V, and Zn.

[0021] The core material contains Ti, Zr, Cr, and V, which improves the strength of the material through solid solution strengthening and dispersion strengthening due to precipitation of intermetallic compounds. The Ti content is 0.005% to 0.30% by mass, the Zr content is 0.005% to 0.30% by mass, the Cr content is 0.005% to 0.30% by mass, and the V content is 0.001% to 0.30% by mass. If the contents of Ti, Zr, Cr, and V are less than the lower limits, the desired strength improvement effect cannot be obtained. If the contents exceed the upper limits, large intermetallic compounds are formed during casting, reducing manufacturability.

[0022] The core material contains Zn, which increases the number of corrosion initiation points and suppresses the localized progression of corrosion in the depth direction. The Zn content is 0.005% by mass or more and 1.0% by mass or less. If the Zn content is less than 0.005% by mass, the desired effect cannot be obtained. On the other hand, if the Zn content exceeds 1.0% by mass, the self-corrosion rate increases, resulting in a decrease in corrosion resistance.

[0023] [Brazing material] The brazing filler metal is an aluminum alloy containing Si and Fe, with the balance being Al and unavoidable impurities.

[0024] Si: 2.0 mass% or more and 13 mass% or less The inclusion of Si in brazing filler metal lowers the melting point and generates a liquid phase at the brazing temperature, making brazing possible. If the Si content is less than 2.0 mass%, the amount of liquid phase generated is small, resulting in poor brazing. If the Si content exceeds 13 mass%, erosion occurs due to excess Si.

[0025] Fe: 0.05 mass% or more and 0.8 mass% or less The inclusion of Fe in brazing filler metal allows for finer grains and ensures fluidity. Fe content less than 0.05% by mass is ineffective, while Fe content greater than 0.8% by mass generates coarse intermetallic compounds, making manufacturing difficult.

[0026] The brazing filler metal may further contain at least one element selected from the group consisting of Zn, Cu, Mn, Cr, V, Zr, Ti, Ni, Mg, and Bi.

[0027] Zn: 5.0% by mass or less When the brazing filler metal contains Zn, it becomes less noble and acts as a sacrificial anode, acting as a corrosion protection layer for the core material. If the Zn content exceeds 5.0 mass%, the corrosion rate becomes too fast.

[0028] The Cu content is 1.0% by mass or less, the Mn content is 2.0% by mass or less, the Cr content is 0.50% by mass or less, the V content is 0.30% by mass or less, the Zr content is 0.30% by mass or less, the Ti content is 0.30% by mass or less, the Ni content is 1.5% by mass or less, the Mg content is 2.0% by mass or less, and the Bi content is 1.0% by mass or less. Note that Mg is contained in the brazing filler metal when used for vacuum brazing, etc. If the Cu and Mg contents exceed the above limits, the material becomes hard and manufacturing becomes difficult. If the Mn, Cr, V, Zr, Ti, and Ni contents exceed the above limits, coarse compounds are formed, making manufacturing difficult. The brazing filler metal may be manufactured without adding Zn, Cu, Mn, Cr, V, Zr, Ti, Ni, Mg, and Bi.

[0029] [Sacrificial material] The sacrificial material is an aluminum alloy containing at least one element selected from the group consisting of Zn, Si, Fe, Cu, Mn, Cr, V, Zr, Ti, Ni, Mg, and Bi, with the remainder being Al and unavoidable impurities.

[0030] Zn: 0.4% by mass or more and 10.0% by mass or less Zn is contained to make the potential more base and thus to obtain a sacrificial anode effect for the core material. If the Zn content is less than 0.4 mass%, the effect is small, but if the Zn content exceeds 10.0 mass%, the corrosion rate becomes too fast, causing the sacrificial material to be consumed early, and the sacrificial anode effect cannot be maintained for a long period of time.

[0031] The Si content is 1.5% by mass or less, the Fe content is 0.8% by mass or less, the Cu content is 1.0% by mass or less, the Mn content is 2.0% by mass or less, the Cr content is 0.50% by mass or less, the V content is 0.30% by mass or less, the Zr content is 0.30% by mass or less, the Ti content is 0.30% by mass or less, the Ni content is 1.5% by mass or less, the Mg content is 3.0% by mass or less, and the Bi content is 1.0% by mass or less. If the Si content exceeds the above range, the melting point decreases and local melting occurs. Mg is contained in the sacrificial material when used for vacuum brazing, etc. If the Cu and Mg contents exceed the above range, the material becomes hard and manufacturing becomes difficult. If the Mn, Cr, V, Zr, Ti, and Ni contents exceed the above range, coarse compounds are formed, making manufacturing difficult. The sacrificial material may be produced without the addition of Si, Fe, Cu, Mn, Cr, V, Zr, Ti, Ni, Mg, and Bi.

[0032] The clad material preferably has a clad structure of any one of the following (a) to (g). (i) It is a single-sided clad type in which the brazing material and the core material are laminated in this order. (b) A double-sided clad type in which the brazing material / the core material / the brazing material are laminated in this order. (c) A double-sided clad type in which the brazing material / the core material / the sacrificial material are laminated in this order. (d) A double-sided clad type in which the brazing material / the core material / the sacrificial material / the brazing material are laminated in this order. (e) A double-sided clad type in which the brazing material / the sacrificial material / the core material / the sacrificial material / the brazing material are laminated in this order. (f) A single-sided clad type in which the sacrificial material and the core material are laminated in this order. (G) A double-sided clad type in which the sacrificial material / the core material / the sacrificial material are laminated in this order.

[0033] The cladding material is preferably of the O, H1n or H2n temper type. [Effects of the Invention]

[0034] According to the present invention, by controlling the distribution of intermetallic compounds with different average particle sizes in the core material and adjusting the solid solubility evaluation value (=11a+2b+6c+9d) of Mn, Si, Cu, and Mg in the core material, the clad material has excellent formability before brazing heat treatment and high strength after brazing heat treatment. DETAILED DESCRIPTION OF THE INVENTION

[0035] A method for manufacturing a clad material according to an embodiment of the present invention includes an ingot manufacturing process for manufacturing a core ingot, a homogenization process for homogenizing the core ingot, a facing process for facing the core ingot, and a cladding process for assembling a rolled material for a brazing material or a rolled material for a sacrificial material to the core ingot, and then rolling and bonding the core ingot and the rolled material to form a clad material.

[0036] [Ingot manufacturing process] The ingot production process produces core ingots (plate-shaped slabs) by semi-continuous casting. The core ingots are made of an aluminum alloy containing 0.8 to 1.8% by mass of Mn, 0.05 to 1.5% by mass of Si, 0.05 to 0.5% by mass of Fe, 0.05 to 1.5% by mass of Cu, 0.001 to 1.0% by mass of Mg, and the balance being Al and unavoidable impurities. Hereinafter, the range of the Mn content of 0.8 to 1.8% by mass, the Si content of 0.05 to 1.5% by mass, the Fe content of 0.05 to 0.5% by mass, the Cu content of 0.05 to 1.5% by mass, and the Mg content of 0.001 to 1.0% by mass will sometimes be referred to as the basic addition amount range.

[0037] The cooling rate during casting is between 0.1°C / s and 10.0°C / s when cooling from 670°C to 600°C. This cooling rate allows for the adjustment of the average particle size and amount of crystallized particles, which are suitable for controlling the formation of intermetallic compounds with an average particle size of more than 500 nm and less than 1500 nm during the hot rolling process after the ingot production process. If the cooling rate is too fast, exceeding 10.0°C / s, the elements are supersaturated in solid solution, reducing the number of intermetallic compounds that crystallize during casting. On the other hand, if the cooling rate is too slow, less than 0.1°C / s, the intermetallic compounds crystallize too coarsely, which results in insufficient crushing of the coarse intermetallic compounds during the subsequent hot rolling process, resulting in a decrease in intermetallic compounds with an average particle size of more than 500 nm and less than 1500 nm and an increase in coarse intermetallic compounds with an average particle size of more than 1.5 μm.

[0038] To improve the strength of the core material, the core ingot may further contain at least one element selected from Ti, Zr, Cr, and V. For example, the amount of Ti added is 0.005% by mass to 0.30% by mass, the amount of Zr added is 0.005% by mass to 0.30% by mass, the amount of Cr added is 0.005% by mass to 0.30% by mass, the amount of V added is 0.001% by mass to 0.30% by mass, and the amount of Zn added is 0.005% by mass to 1.0% by mass.

[0039] To improve the corrosion resistance of the core material, the core ingot may be made by adding Zn, with the Zn content being 0.005% by mass or more and 1.0% by mass or less.

[0040] [Homogenization process] In the homogenization process, the core ingot is maintained at a heating and holding temperature of 420°C or higher but lower than 550°C. The holding time is 1 hour or higher but 10 hours or lower, and preferably 3 hours or higher but 8 hours or lower. The heating rate from 400°C to the heating and holding temperature is 15°C / h or higher but 60°C / h or lower, and preferably 20°C / h or higher but 40°C / h or lower. The cooling rate from the heating and holding temperature to 400°C is 10°C / h or higher but 50°C / h or lower, and preferably 15°C / h or higher but 40°C / h or lower.

[0041] Homogenization treatment allows elements dissolved during casting to precipitate as intermetallic compounds (particles containing mainly Mn and Si), resulting in a favorable distribution of intermetallic compounds. During homogenization treatment, if the core ingot is maintained at a low temperature below 400°C, fine intermetallic compounds precipitate, whereas if it is maintained at a high temperature above 550°C, coarse intermetallic compounds precipitate. Specifically, if the homogenization temperature is too low, the number of intermetallic compounds with an average particle size greater than 50 nm and less than 100 nm increases excessively. On the other hand, if the homogenization temperature is too high, the number of intermetallic compounds with an average particle size greater than 50 nm and less than 100 nm decreases, and the number of intermetallic compounds with an average particle size greater than 100 nm and less than 300 nm also decreases.

[0042] [Facing process] In the facing process, the top and bottom surfaces of the core ingot are faced to remove segregated areas and oxide films.

[0043] [Clad process] The cladding process includes an assembly process in which rolled material for brazing or sacrificial material is assembled onto a core ingot (plate-shaped slab); a soaking process in which the core ingot and rolled material are heated to 470°C or higher and 530°C or lower and held in this state for 1 hour or higher and 12 hours or lower in order to hot roll them; a hot rolling process in which the core ingot heated in the soaking process and the rolled material are rolled and bonded together to form a thick plate; and a cold rolling process in which the thick plate formed in the hot rolling process is thinned.

[0044] [Hot rolling process] The hot rolling process includes a first hot rolling process, a second hot rolling process after the first hot rolling process, and a cooling process. In both the first hot rolling process and the second hot rolling process, the temperature and the thickness after rolling are controlled within predetermined ranges, and the cooling rate in the second hot rolling process is also controlled within a predetermined range.

[0045] In the first hot rolling process, the starting temperature of the hot rolling is 470°C or more and 520°C or less, and the finishing temperature is 330°C or more and 400°C or less, and the rolled material for the brazing material or sacrificial material and the ingot for the core material are bonded together and roughly rolled into a thick plate with a thickness of 15 mm or more and 30 mm or less.

[0046] In the second hot rolling process, a thick plate with a thickness of 15 mm to 30 mm is rolled at a starting temperature of 340°C to 400°C and an ending temperature of 240°C to 400°C. After the second hot rolling process, the plate is formed into a finished hot-rolled material with a thickness of 1 mm to 4 mm.

[0047] The second hot rolling process is a reverse-type finishing process, and the number of rolling passes in the second hot rolling process is between one and three, with the steel being temporarily wound onto a coil after each pass. The holding time from winding onto a coil until the start of the next rolling pass is controlled to within five minutes.

[0048] In the cooling process, the finally coiled finish hot-rolled material (e.g., after three passes) is cooled in the temperature range from the finishing temperature immediately after the second hot rolling process to 100°C at a cooling rate of 10°C / h or more and 50°C / h or less.

[0049] The hot rolling process also controls the amount of equivalent strain in the finish hot-rolled material formed from the start of hot rolling through the cooling process. Specifically, the thickness of the core ingot and the thickness of the finish hot-rolled material are adjusted so that the equivalent strain ε shown in the following formula (1) is ε > 1.0. ε=(2 / √3)ln(t0 / t) Equation (1) t0: Thickness of the core ingot (slab) at the start of hot rolling t: Thickness of the finished hot-rolled material after the hot rolling process and before the rolling process

[0050] By controlling the heat application to the aluminum alloy for the core material in the hot rolling process, elements that dissolved during casting but did not precipitate during the homogenization treatment can be precipitated as intermetallic compounds, thereby reducing the solid solubility of the added elements. Intermetallic compounds containing Cu, Mg, etc., in particular, can be precipitated in the cooling process after the second hot rolling process. If the cooling rate in the cooling process after the second hot rolling process is too fast (>50°C / h), the precipitation of intermetallic compounds containing Cu and Mg will be insufficient, resulting in a high solid solubility of the elements in the core material. If the cooling rate is too slow (<10°C / h), the precipitates will become coarse, which is undesirable.

[0051] The rolled plates for the brazing material or sacrificial material are made of an aluminum alloy, and the plate thickness is adjusted by hot rolling so as to have a predetermined cladding ratio.

[0052] The aluminum alloy for brazing filler metal contains 2.0 to 13% by mass of Si, 0.05 to 0.8% by mass of Fe, and the remainder being Al and unavoidable impurities. The aluminum alloy for brazing filler metal may further contain at least one element selected from the group consisting of Zn, Cu, Mn, Cr, V, Zr, Ti, Ni, Mg, and Bi. For example, the Zn content is 5.0% by mass or less, the Cu content is 1.0% by mass or less, the Mn content is 2.0% by mass or less, the Cr content is 0.50% by mass or less, the V content is 0.30% by mass or less, the Zr content is 0.30% by mass or less, the Ti content is 0.30% by mass or less, the Ni content is 1.5% by mass or less, the Mg content is 2.0% by mass or less, and the Bi content is 1.0% by mass or less.

[0053] The aluminum alloy for the sacrificial material contains at least one element selected from the group consisting of Zn, Si, Fe, Cu, Mn, Cr, V, Zr, Ti, Ni, Mg, and Bi, with the remainder consisting of Al and unavoidable impurities. For example, the Zn content is 0.4% to 10.0% by mass, the Si content is 1.5% by mass or less, the Fe content is 0.8% by mass or less, the Cu content is 1.0% by mass or less, the Mn content is 2.0% by mass or less, the Cr content is 0.50% by mass or less, the V content is 0.30% by mass or less, the Zr content is 0.30% by mass or less, the Ti content is 0.30% by mass or less, the Ni content is 1.5% by mass or less, the Mg content is 3.0% by mass or less, and the Bi content is 1.0% by mass or less.

[0054] The finished hot-rolled material then undergoes a cold rolling process to complete the clad material. The clad material is layered in the order of brazing material / core material, or sacrificial material / core material. The clad material is not limited to a single-sided clad type in which at least one of the brazing material and the sacrificial material is clad on one side of the core material, but may be configured as a double-sided clad type in which at least one of the brazing material and the sacrificial material is clad on both sides of the core material. The clad configuration of the double-sided clad type is, for example, any of the following (a1) to (a5). (a1) The layers are laminated in the order of brazing material / core material / brazing material. (a2) The brazing material, core material, and sacrificial material are layered in this order. (a3) The layers are layered in the order of brazing material / core material / sacrificial material / brazing material. (a4) The layers are layered in the following order: brazing material / sacrificial material / core material / sacrificial material / brazing material. (a5) The layers are stacked in the order of sacrificial material / core material / sacrificial material. The single-sided clad mold may be laminated in the order of brazing material / sacrificial material / core material.

[0055] In both the single-sided clad type and the double-sided clad type, the clad ratio, which indicates the percentage of the thickness of the core material in the total thickness of the clad material, is set to 71% or more and 97% or less.

[0056] If necessary, intermediate annealing may be performed on the finish hot-rolled material after the hot rolling process, and final annealing may be performed on the clad material after the cold rolling process. Intermediate annealing may involve holding the material at a temperature of 200°C to 450°C for 1 hour to 12 hours. Final annealing may involve holding the material at a temperature of 200°C to 450°C for 1 hour to 12 hours. If only intermediate annealing is performed on the clad material, it will be tempered H1n, and if final annealing is performed, it will be tempered H2n or O depending on the annealing conditions.

[0057] The clad material produced in this manner is used as a material for forming parts such as, but not limited to, headers and tubes for automobile heat exchangers, and further, parts made of the clad material are brazed together by brazing heat treatment to form heat exchangers.

[0058] [Distribution of intermetallic compounds] The core material of the clad material before the brazing heat treatment is in a state in which the intermetallic compounds are distributed in an appropriate number for each average particle size by controlling the cooling rate of the core ingot during casting to a predetermined value and further controlling the heat application during the homogenization treatment and hot rolling. In the clad material of this embodiment, the number of intermetallic compounds is measured in a cross section (hereinafter sometimes referred to as an RD-TD parallel cross section) of the core material before the brazing heat treatment, which is parallel to the rolling direction (hereinafter sometimes referred to as RD) and the transverse direction (hereinafter sometimes referred to as TD), which are perpendicular to the thickness direction (normal direction).

[0059] The number of intermetallic compounds with an average particle size of more than 50 nm and less than 100 nm is 0.5 × 10 6 pieces / mm 2 Over 6.0 x 10 6 pieces / mm 2 Intermetallic compounds with an average grain size of more than 50 nm and less than 100 nm, with a controlled distribution in this way, interact with dislocations introduced during deformation such as working, improving work hardening ability and thereby formability.

[0060] The number of intermetallic compounds with an average particle size of more than 100 nm and less than 300 nm is 1.0 × 10 6 pieces / mm 2 Over 5.0 x 10 6 pieces / mm 2 Intermetallic compounds with an average particle size of more than 100 nm and not more than 300 nm, which have such a controlled distribution, are less likely to re-dissolve during brazing and can maintain a fine state, which contributes to improving the strength of the core material after brazing.

[0061] The number of intermetallic compounds with an average particle size of more than 500 nm and less than 1500 nm is 5.0 × 10 3 pieces / mm 2 Over 15.0 x 10 3 pieces / mm 2Intermetallic compounds with an average grain size of more than 500 nm and not more than 1500 nm, whose distribution is controlled in this way, average out strain concentrations and make deformation uniform.

[0062] In the RD-TD parallel cross section of the core material of the clad material before brazing heat treatment, the distribution of intermetallic compounds was measured. The number of intermetallic compounds with an average particle size of more than 50 nm and less than 100 nm was 0.5 × 10 6 pieces / mm 2 Over 6.0 x 10 6 pieces / mm 2 and the number of intermetallic compounds with an average particle size of more than 100 nm and less than 300 nm is 1.0 × 10 6 pieces / mm 2 Over 5.0 x 10 6 pieces / mm 2 and the number of intermetallic compounds having an average particle size of more than 500 nm and 1500 nm or less is 5.0 × 10 3 pieces / mm 2 Over 15.0 x 10 3 pieces / mm 2 Hereinafter, the above-mentioned condition will be referred to as "the distribution of intermetallic compounds is in the optimum range."

[0063] [Solid solubility of Mn, Si, Cu and Mg] Furthermore, the solid solubility of the core material of the clad material before brazing heat treatment, as determined by inductively coupled plasma atomic emission spectroscopy, is determined as follows: the solid solubility of Mn is a mass%, the solid solubility of Si is b mass%, the solid solubility of Cu is c mass%, and the solid solubility of Mg is d mass%, and the solid solubility evaluation value is 11a + 2b + 6c + 9d. The solid solubility of each element is determined by inductively coupled plasma atomic emission spectroscopy after dissolving at least a portion of the core material in hot phenol and filtering the solution through a 0.2 μm mesh filter. The filtered solution mainly contains the base material and the solute elements.

[0064] The solid solubility evaluation value is a parameter that indicates the degree of influence of the interaction between each element (Mn, Si, Cu, and Mg) and dislocations, and when the solid solubility evaluation value is less than 9.0 mass%, the formability of the clad material, which is capable of being deformed into a desired shape, is improved. When the solid solubility evaluation value is 9.0 mass% or more, the total content of multiple solid solution elements (Mn, Si, Cu, and Mg) is high, which reduces formability.

[0065] [Elongation before brazing heat treatment] The elongation of the clad material measured by the butt joint method on the JIS No. 5 test piece before brazing heat treatment is 20% or more for O material, 2% or more for H14 material, and 15% or more for H24 material.

[0066] [Strength after brazing heat treatment] In addition, the tensile strength of the JIS No. 5 test piece of the clad material after brazing heat treatment is 140 MPa or more.

[0067] The core material of the clad material of this embodiment has a metal structure in which the content of each element is controlled and the distribution of intermetallic compounds for each average particle size in the RD-TD parallel cross section is controlled to adjust the solid solubility evaluation value (=11a+2b+6c+9d) for the elements (Mn, Si, Cu, and Mg), thereby improving the formability of the core material before brazing heat treatment and the strength after brazing heat treatment. Furthermore, since the clad ratio of the core material is 71% or more and 97% or less, the formability and strength of the clad material are improved as well as the formability and strength of the core material. [Example]

[0068] The clad materials were prepared by varying the content of each element in the core ingot and the cooling rate of the core ingot, as well as by varying the heat application method during the homogenization treatment of the core ingot and the hot rolling when cladding with brazing material or sacrificial material. The distribution of intermetallic compounds in the core material of each sample, the solid solubility evaluation value of Mn, Si, Cu, and Mg (= 11a + 2b + 6c + 9d), the elongation of the clad material before heat treatment equivalent to brazing, and the strength of the clad material after heat treatment equivalent to brazing were confirmed.

[0069] The core ingot, brazing filler ingot, and sacrificial ingot were made of aluminum alloy produced by semi-continuous casting. The brazing filler ingot and sacrificial ingot were cast under conventional manufacturing conditions. The brazing filler ingot and sacrificial ingot were made from rolled plates whose thickness was adjusted by hot rolling to achieve the specified cladding ratio.

[0070] The core ingots were subjected to a predetermined homogenization treatment, followed by surface grinding. Then, rolled plates for the brazing material and / or sacrificial material were assembled onto the core ingots, and the resulting mixture was heated to 500°C for one hour as a soaking treatment. After the soaking treatment, the ingots were hot-rolled, and then cold-rolled to a thickness of 0.5 mm. After cold rolling, final annealing was performed to obtain the final materials (samples) (O material, H2n material). For some samples, the final annealing was performed just before 0.5 mm, and samples were also prepared in which the thickness was reduced to 0.5 mm so that the cold-rolling reduction was 40% (temper H1n material).

[0071] The clad structure of each sample, the clad ratio of the core material, brazing material, and sacrificial material, the content of each added element in the core material, brazing material, and sacrificial material, and the quality of the clad material are shown in Table 1. Each sample is a single-sided clad type, and samples 3 to 5 are constructed by laminating the core material, brazing material, and sacrificial material in that order.

[0072] The cooling rate during casting of the core ingot for each sample, the manufacturing conditions for the homogenization treatment of the core ingot, and the manufacturing conditions for hot rolling when cladding the brazing filler metal and the sacrificial material are shown in Table 2. The manufacturing conditions for the homogenization treatment are the heating holding temperature and holding time for holding the core ingot in a heated state for the homogenization treatment, the heating rate for raising the temperature from 400°C to the heating holding temperature, and the cooling rate for cooling from the heating holding temperature to 400°C. The hot rolling process includes a first hot rolling process in which rolled materials for the brazing material and / or sacrificial material are assembled with a core ingot and then roughly rolled to form a bonded thick plate; a second hot rolling process in which the thick plate is rolled at a temperature lower than the temperature of the first hot rolling process to form a thinner finish hot-rolled material; and a cooling process in which the finish hot-rolled material is cooled from the temperature immediately after the second hot rolling process to 100°C. The manufacturing conditions are the start and end temperatures of the first and second hot rolling processes, respectively, the cooling rate of the cooling process, and the equivalent strain ε of the finish hot-rolled material shown in formula (1).

[0073] [Table 1]

[0074] [Table 2]

[0075] [Evaluation items] 1. Distribution of intermetallic compounds 1-1. Intermetallic compounds with an average particle size of more than 50 nm and less than 100 nm The RD-TD parallel cross section of the clad material was subjected to cross-section polishing, and a secondary electron image of the RD-TD parallel cross section was taken at a magnification of 10,000 times using a scanning electron microscope (area: 12 μm 2 ) was obtained. Using image analysis software, the number of intermetallic compounds with an average particle size of more than 50 nm and less than 100 nm per unit area was determined from the obtained images. Ten fields of view were observed and the number was determined for each, and the average of these was used as the measurement value.

[0076] 1-2. Intermetallic compounds with an average particle size of more than 100 nm and less than 300 nm Using the same procedure as in the measurement method 1-1 above, the distribution of intermetallic compounds with a size of more than 100 nm and not more than 300 nm was observed in 10 visual fields, and the average value was calculated from the number per unit area obtained in each visual field, and this was used as the measurement value.

[0077] 1-3. Intermetallic compounds with an average particle size of more than 500 nm and less than 1500 nm The RD-TD parallel cross section of the clad material was mechanically polished, and a secondary electron image of the cross section was taken at a magnification of 1000 times using a scanning electron microscope (area: 3500 μm 2 ) was obtained. Image analysis software was used to determine the number of intermetallic compounds with an average particle size of more than 500 nm and less than 1500 nm from the obtained images. Ten fields of view were observed, and the number per unit area in each field of view was determined, and the average of these was used as the measured value. Table 3 shows the number of intermetallic compounds by particle size in each sample.

[0078] 2.Solid solubility of Mn, Si, Cu and Mg Before brazing-equivalent heat treatment, the clad material was etched to remove the skin, and the core material was dissolved in hot phenol. The solution was then filtered through a 0.2 μm mesh filter, and the extracted solution was analyzed by inductively coupled plasma atomic emission spectroscopy. The solid solubility of Mn (mass%), (mass%), Si (mass%), (mass%), Cu (mass%), and Mg (mass%) were measured. These measurements were used to calculate the solid solubility evaluation value (= 11a + 2b + 6c + 9d). Table 3 shows the solid solubility evaluation values ​​for each sample.

[0079] 3. Elongation of clad material Before brazing-equivalent heat treatment, JIS No. 5 test pieces were taken from the clad material at an angle of 0° to the rolling direction (RD). Tensile tests were conducted at room temperature, and total elongation was measured using the butt joint method. Elongation was evaluated as 20% or more for O material, 2% or more for H14 material, and 15% or more for H24 material. Table 3 shows the elongation evaluation for each sample, with A indicating a pass and B indicating a fail.

[0080] 4. Strength of clad material (tensile strength) JIS No. 5 test pieces were taken from the clad material, which had been subjected to heat treatment equivalent to brazing, at a direction 0° to the rolling direction (RD), and tensile tests were conducted at room temperature to measure tensile strength. The heat treatment equivalent to brazing involved heating to 600°C at a heating rate of 50°C / min, holding at 600°C for 3 minutes, and then cooling to 300°C at a cooling rate of 100°C / min. A tensile strength of 140 MPa or more was considered to have passed. Table 3 shows the strength evaluation of each sample, with A indicating a pass and B indicating a fail.

[0081] 5. Overall Judgment The samples that passed both the elongation evaluation and the strength evaluation were judged to be "pass." Table 3 shows the overall evaluation of each sample, with A indicating "pass" and B indicating "fail."

[0082] [Table 3]

[0083] In Samples 1 to 5, the cladding ratio of the core material was set to 71% or more and 97% or less, and the core material was made of an aluminum alloy with the contents of Mn, Si, Fe, Cu, and Mg falling within the basic content ranges. Furthermore, the core materials of Samples 1 to 5 were manufactured by controlling the cooling of the core ingot during casting, the homogenization treatment of the core ingot, and the heat application during hot rolling to bond the core to the skin material. Before the brazing-equivalent heat treatment, the distribution of intermetallic compounds in the core material was controlled within an optimal range, and the solid solubility evaluation value (= 11a + 2b + 6c + 9d) for the elements (Mn, Si, Cu, and Mg) was adjusted to less than 9.0 mass%. As a result, the formability evaluation before the brazing-equivalent heat treatment and the strength evaluation after the brazing-equivalent heat treatment were both A (pass), resulting in an overall evaluation of A (pass).

[0084] In Sample 6, the core material has a cladding ratio of 90%, and is made of an aluminum alloy with the contents of Mn, Si, Fe, Cu, and Mg falling within the basic content ranges. However, the cooling rate of the core ingot during casting exceeds 10°C / h, and the heating holding temperature during the homogenization treatment of the core ingot exceeds 550°C, with a cooling rate higher than 50°C / h. Furthermore, in the hot rolling process, the end temperature of the first hot rolling step exceeds 400°C, and the start temperature and end temperature of the second hot rolling step also exceed 400°C, and the cooling rate also exceeds 50°C / h. Thus, the core material of Sample 6 is not as well controlled as the manufacturing methods of Samples 1 to 5 in terms of the cooling of the core ingot during casting, the homogenization treatment of the core ingot, and the heat application during hot rolling to bond the skin material. As a result, the distribution of intermetallic compounds in the core material of the clad material was not adjusted to the optimal range before the heat treatment equivalent to brazing, and the solid solubility evaluation value (= 11a + 2b + 6c + 9d) was large, resulting in a dense distribution of multiple elements. In particular, there were few intermetallic compounds with an average particle size of more than 50 nm and less than 100 nm, and the formability was evaluated as B (fail). Furthermore, the core material of sample 6 had a small number of intermetallic compounds with an average particle size of more than 100 nm and less than 300 nm, so the strength after the heat treatment equivalent to brazing was evaluated as B (fail).

[0085] The core material of Sample 7 was manufactured under the same conditions as Samples 1 to 5, including the cooling of the core ingot during casting, the homogenization treatment of the core ingot, and the heat application during hot rolling to bond the cladding material. The core material had a cladding ratio of 90% and was made of an aluminum alloy with Si, Fe, Cu, and Mg contents within the basic content ranges, but with a Mn content exceeding 1.8% by mass. In Sample 7, before the brazing-equivalent heat treatment, the distribution of intermetallic compounds was not adjusted to the optimal range, resulting in a large solid solubility evaluation value (= 11a + 2b + 6c + 9d) and a dense distribution of multiple elements. In particular, the number of intermetallic compounds with an average particle size greater than 50 nm but less than 100 nm was low, resulting in Sample 7 receiving a formability evaluation of B (fail). The strength of sample 7 after the heat treatment equivalent to brazing was evaluated as A (pass), but the formability was evaluated as B (fail), so the overall evaluation was B (fail).

Claims

1. An aluminum alloy clad material in which a skin material made of at least one of a brazing material and a sacrificial material is clad on one or both sides of a core material, The cladding ratio of the core material is 71% or more and 97% or less, the core material contains 0.8% by mass or more and 1.8% by mass or less of Mn, 0.05% by mass or more and 1.5% by mass or less of Si, 0.05% by mass or more and 0.5% by mass or less of Fe, 0.05% by mass or more and 1.5% by mass or less of Cu, 0.001% by mass or more and 1.0% by mass or less of Mg, and the balance being Al and unavoidable impurities; In a cross section of the core material before brazing heat treatment, which is parallel to the rolling direction and a transverse direction perpendicular to the rolling direction and the thickness direction, the density of intermetallic compounds having an average particle size of more than 50 nm and not more than 100 nm is 0.5×10 ６ pieces / mm ２ Above 6.0 x 10 ６ pieces / mm ２ and the density of the intermetallic compound having an average particle size of more than 100 nm and 300 nm or less is 1.0 × 10 ６ pieces / mm ２ Above 5.0 x 10 ６ pieces / mm ２ and the density of the intermetallic compound having an average particle size of more than 500 nm and 1500 nm or less is 5.0 × 10 ３ pieces / mm ２ Above 15.0 x 10 ３ pieces / mm ２ is as follows: Furthermore, the core material before brazing heat treatment has a solid solubility of Mn of a mass%, a solid solubility of Si of b mass%, a solid solubility of Cu of c mass%, and a solid solubility of Mg of d mass%, and further, when the solid solubility evaluation value is 11a + 2b + 6c + 9d, the solid solubility evaluation value is less than 9.0 mass%.

2. The clad material of claim 1, characterized in that the core material further contains at least one element from the group consisting of Ti in an amount of 0.005 mass% to 0.30 mass%; Zr in an amount of 0.005 mass% to 0.30 mass%; Cr in an amount of 0.005 mass% to 0.30 mass%; V in an amount of 0.001 mass% to 0.30 mass%; and Zn in an amount of 0.005 mass% to 1.0 mass%.

3. The brazing filler metal contains 2.0 mass % or more and 13 mass % or less of Si, 0.05 mass % or more and 0.8 mass % or less of Fe, and the balance being Al and unavoidable impurities, 3. The clad material according to claim 1 or 2, characterized in that the sacrificial material contains at least one element selected from the group consisting of 1.5 mass% or less Si, 0.8 mass% or less Fe, 0.4 mass% to 10.0 mass% Zn, 1.0 mass% or less Cu, 2.0 mass% or less Mn, 0.50 mass% or less Cr, 0.30 mass% or less V, 0.30 mass% or less Zr, 0.30 mass% or less Ti, 1.5 mass% or less Ni, 3.0 mass% or less Mg, and 1.0 mass% or less Bi, with the remainder consisting of Al and unavoidable impurities.

4. the brazing filler metal contains 2.0 mass% or more and 13 mass% or less of Si, 0.05 mass% or more and 0.8 mass% or less of Fe, and at least one element selected from 5.0 mass% or less of Zn, 1.0 mass% or less of Cu, 2.0 mass% or less of Mn, 0.50 mass% or less of Cr, 0.30 mass% or less of V, 0.30 mass% or less of Zr, 0.30 mass% or less of Ti, 1.5 mass% or less of Ni, 2.0 mass% or less of Mg, and 1.0 mass% or less of Bi, with the remainder being Al and unavoidable impurities; 3. The clad material according to claim 1 or 2, characterized in that the sacrificial material contains at least one element selected from the group consisting of 1.5 mass% or less Si, 0.8 mass% or less Fe, 0.4 mass% to 10.0 mass% Zn, 1.0 mass% or less Cu, 2.0 mass% or less Mn, 0.50 mass% or less Cr, 0.30 mass% or less V, 0.30 mass% or less Zr, 0.30 mass% or less Ti, 1.5 mass% or less Ni, 3.0 mass% or less Mg, and 1.0 mass% or less Bi, with the remainder consisting of Al and unavoidable impurities.

5. The clad material according to claim 1 or claim 2, characterized in that the clad structure is any one of the following (i) to (g). (i) It is a single-sided clad type in which the brazing material and the core material are laminated in this order. (b) A double-sided clad type in which the brazing material / the core material / the brazing material are laminated in this order. (c) A double-sided clad type in which the brazing material / the core material / the sacrificial material are laminated in this order. (d) A double-sided clad type in which the brazing material / the core material / the sacrificial material / the brazing material are laminated in this order. (e) A double-sided clad type in which the brazing material / the sacrificial material / the core material / the sacrificial material / the brazing material are laminated in this order. (f) It is a single-sided clad type in which the sacrificial material and the core material are laminated in this order. (G) It is a double-sided clad type in which the sacrificial material / the core material / the sacrificial material are laminated in this order.

6. 3. The clad material according to claim 1, characterized in that its temper is one of O, H1n and H2n.

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