阅读说明：本技术 铝合金钎焊片材 (Aluminum alloy brazing sheet ) 是由 丸野瞬 吉野路英 岩尾祥平 于 2019-08-19 设计创作，主要内容包括：本发明提供一种铝合金钎焊片材,其在芯材的至少一个表面上具有保持钎料的功能的牺牲材料,所述牺牲材料具有如下组成：以质量％含有Si：2～5％、Zn：3～5％,剩余部分由Al及不可避免的杂质组成,所述芯材由Al-Mn系合金组成,在钎焊前的芯材中,当量圆直径为100～400nm的Al-Mn系第二相粒子以0.3～5个/μm～2的数密度分布。(The present invention provides an aluminum alloy brazing sheet having a sacrificial material having a function of holding a brazing filler metal on at least one surface of a core material, the sacrificial material having a composition as follows: contains, in mass%, Si: 2-5%, Zn: 3 to 5% and the balance of Al and inevitable impurities, wherein the core material is made of an Al-Mn alloy, and the number of Al-Mn second phase particles having an equivalent circle diameter of 100 to 400nm in the core material before brazing is 0.3 to 5 particles/μm 2 Number density distribution of (2).)

1. An aluminum alloy brazing sheet having a sacrificial material having a function of holding a brazing filler metal on at least one surface of a core material, wherein,

the sacrificial material has the following composition: contains, in mass%, Si: 2.0-5.0%, Zn: 3.0 to 5.0%, the remainder consisting of Al and unavoidable impurities,

the core material is made of an Al-Mn alloy, and the number of Al-Mn second phase particles having an equivalent circle diameter of 100 to 400nm is 0.3 to 5/μm in the core material before brazing²Number density distribution of (2).

2. The aluminum alloy brazing sheet of claim 1,

after brazing equivalent heat treatment at a temperature of 590 to 615 ℃, the Mn/Si ratio in a region of 50 μm in the depth direction of the core from the sacrificial material/core interface is 0.5 to 5.0.

3. The aluminum alloy brazing sheet according to claim 1 or 2,

the core material has the following composition: contains, in mass%, Mn: 0.3-2.0%, Si: 0.05 to 1.0%, Cu: 0.01 to 1.0%, Fe: 0.1 to 0.7%, and the balance of Al and unavoidable impurities.

4. The aluminum alloy brazing sheet according to any one of claims 1 to 3,

the sacrificial material further contains, in mass%, Mn: 0.1 to 1.0%, Fe: 0.1-0.7% of one or more than two.

5. The aluminum alloy brazing sheet of any one of claims 1 to 4,

and the cavitation potential after brazing is reduced according to the sequence of eutectic brazing of the sacrificial material, primary brazing of the sacrificial material and an interface layer of the sacrificial material/core material, and the potential difference between the highest layer in the sacrificial material and the lowest layer in the core material is 50-200 mV.

Technical Field

The present invention relates to an aluminum alloy brazing sheet having a sacrificial material having a function of holding a brazing filler metal on at least one surface of a core material.

Background

In recent years, there has been an increasing demand for heat exchangers for automobiles for cooling fluids such as engines and engine oils. In these heat exchangers, cooling is performed with water (+ Long Life Coolant: LLC), and since it is a corrosive environment, high corrosion resistance is required on the cooling water flow side.

Further, since the heat exchanger for an automobile needs to be joined to each other by brazing heat treatment, a brazing sheet composed of a sacrificial material, a core material, and a brazing filler metal is often used for this purpose. However, the heat exchanger used in such applications takes various forms, and may also have a complicated structure, and thus there is a problem in that the structure is limited in the case where there is no brazing filler metal layer or only one brazing filler metal layer. Further, corrosion resistance may be required on the side to be brazed.

In recent years, an Al — Zn — Si alloy is known in which one-side sacrificial material has a function of a brazing material (for example, refer to patent document 1).

Prior art documents

Patent document

Patent document 1: japanese patent laid-open publication No. 2005-307251

Disclosure of Invention

Technical problem to be solved by the invention

However, in the Al-Zn-Si alloy in which the sacrificial material functions as a brazing material, the Si concentration in the Al-Zn-Si alloy is suppressed to a certain extent to be low in order to maintain the effect of the sacrificial material, and thus it is necessary to secure corrosion resistance by primary crystals remaining after brazing. However, conventionally, there have been problems such as occurrence of grain boundary corrosion and accompanying detachment of primary crystals as an anti-corrosion layer depending on the distribution state of Al — Mn-based second phase particles in the core material.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an aluminum alloy brazing sheet having excellent corrosion resistance and brazeability.

Means for solving the technical problem

In the present invention, Si is contained in the sacrificial material to function as a brazing material, whereby the heat exchanger having a complicated structure can be handled, and corrosion resistance on the cooling water side can be ensured.

Further, by controlling the equivalent circle diameter and the number density of the dispersed particles in the core material and controlling the precipitation site of free Si diffusing from the sacrificial material into the core material, Si precipitation at grain boundaries, formation of a Si thin layer near the grain boundaries, and grain boundary corrosion are suppressed, and corrosion resistance is improved.

That is, the aluminum alloy brazing sheet of the present invention is the aluminum alloy brazing sheet of the 1 st aspect which has a sacrificial material having a function of holding a brazing material on at least one surface of a core material,

the sacrificial material has the following composition: contains, in mass%, Si: 2.0-5.0%, Zn: 3.0 to 5.0%, the remainder consisting of Al and unavoidable impurities,

the core material is made of an Al-Mn alloy, and the number of Al-Mn second phase particles having an equivalent circle diameter of 100 to 400nm is 0.3 to 5/μm in the core material before brazing²Number density distribution of (2).

In another aspect of the invention, after the brazing equivalent heat treatment for raising the temperature to 590 to 615 ℃, the Mn/Si ratio in a region of 50 μm in the depth direction of the core from the sacrificial material/core interface is 0.5 to 5.0.

In another aspect of the invention of the aluminum alloy brazing sheet, the core material has the following composition: contains, in mass%, Mn: 0.3-2.0%, Si: 0.05 to 1.0%, Cu: 0.01 to 1.0%, Fe: 0.1 to 0.7%, and the balance of Al and unavoidable impurities.

Another aspect of the invention of an aluminum alloy brazing sheet in another aspect of the invention, the sacrificial material further contains, in mass%, Mn: 0.1 to 1.0%, Fe: 0.1-0.7% of one or more than two.

In another aspect of the invention of an aluminum alloy brazing sheet, a pitting potential after brazing is lowered in the order of eutectic brazing of a sacrificial material, primary brazing of a sacrificial material, and a sacrificial material/core material interface layer, and a potential difference between the highest layer of the sacrificial material and the lowest layer of the core material is 50 to 200 mV.

The reasons for limiting the technical matters defined in the present invention will be described below. The content of the components contained in the sacrificial material and the core material is expressed by mass%.

[ sacrificial Material ]

Si: 2.0 to 5.0% (preferably 2.5 to 4.0%)

Si is contained as an essential element for improving the brazing property. However, if the content is too small, poor bonding is caused, and if the content is too large, corrosion occurs and corrosion resistance is deteriorated. For these reasons, the Si content is defined within the above range. For the same reason, the lower limit of the Si content is desirably 2.5% and the upper limit is desirably 4.0%.

Zn: 3.0 to 5.0% (preferably 3.0 to 4.0%)

Zn is contained as an essential element for improving corrosion resistance. However, if the content is too small, the corrosion resistance is deteriorated, and if the content is too large, the fillet is preferentially corroded. For these reasons, the Zn content is defined to be within the above range. For the same reason, the lower limit of the Zn content is desirably 3.0% and the upper limit is desirably 4.0%.

Mn: 0.1 to 1.0% (preferably 0.2 to 0.8%)

Mn is contained as necessary for improving the strength. However, if the content is small, the desired effect cannot be obtained, and if the content is too large, a huge intermetallic compound is generated. For these reasons, when Mn is contained, it is desirable that the Mn content is within the above range. For the same reason, the lower limit of the Mn content is desirably 0.2% and the upper limit is desirably 0.8%. Even when Mn is not positively contained, 0.05% or less of Mn may be contained as an inevitable impurity.

Fe: 0.1 to 0.7% (preferably 0.1 to 0.5%)

Fe is contained as needed because of its improved strength. However, if the content is small, the desired effect cannot be obtained, and if the content is too large, a large intermetallic compound is generated at the time of casting, and corrosion resistance is deteriorated. For these reasons, when Fe is contained, it is desirable that the Fe content be within the above range. For the same reason, it is desirable that the lower limit of the Fe content is 0.1% and the upper limit is 0.5%. Even when Fe is not positively contained, 0.05% or less of Fe may be contained as an inevitable impurity.

Equivalent circle diameter of Al-Mn-based second phase particles: 100 to 400nm (preferably 150 to 300nm)

The number density of the Al-Mn based second phase particles is 0.3 to 5 particles/μm²(preferably 0.4 to 3.5 pieces/μm)²)

The equivalent circle diameter and number density of the Al-Mn based second phase particles must be controlled to be compatible with corrosion resistance and corrosion inhibition. There is a trade-off relationship between the equivalent circle diameter and the number density, and basically, in the case where the equivalent circle diameter is small, the number density increases. If the circle equivalent diameter is small and the number density is too large, recrystallization behavior of the core material at the time of brazing is delayed, and thus corrosion occurs and brazing failure occurs. If the circle equivalent diameter is large and the number density is small (the amount of Si dissolved increases due to re-solution), grain boundary corrosion occurs due to excessive free Si, and the corrosion resistance deteriorates.

For these reasons, it is desirable that the equivalent circle diameter and the number density of the Al-Mn based second phase particles are within the above ranges. For the same reason, the lower limit of the equivalent circle diameter of the Al-Mn based second phase particles is desirably 150nm, the upper limit thereof is desirably 300nm, and the lower limit of the number density of the Al-Mn based second phase particles is desirably 0.4 particles/. mu.m²The upper limit is set to 3.5 pieces/. mu.m²。

In order to control the distribution state of these Al — Mn-based second phase particles, it is necessary to appropriately combine the homogenization treatment, hot rolling, and annealing temperature conditions. The homogenization treatment is preferably performed by heating the ingot at a treatment temperature of 400 to 600 ℃ for 5 to 20 hours to control the precipitation of the second phase particles. The higher the treatment temperature and the longer the treatment time, the larger the size and the lower the density of the second phase particles tend to be. Since the hot rolling temperature and the final annealing condition tend to be the same, the hot rolling completion temperature and the final annealing condition are appropriately controlled. Preferably, the annealing is performed at a finish hot rolling temperature of 400 ℃ to 450 ℃ inclusive and a finish annealing temperature of 350 ℃ to 350 ℃. However, since the dispersion state of the second phase particles also varies depending on these combinations, it is necessary to appropriately combine and select these process conditions in order to obtain a dispersion state of the second phase particles in the above-described range.

[ core Material ]

An Al-Mn alloy is used as the core material. The following components are described as preferred components, but the present invention is not limited to the following components.

Mn: 0.3 to 2.0% (preferably 0.5 to 2.0%)

Mn is an essential element for improving strength. However, if the content is small, the desired effect cannot be sufficiently obtained, and if the content is too large, the manufacturability (castability, rolling ability) is deteriorated. For these reasons, it is desirable that the Mn content is set within the above range. For the same reason, it is desirable that the lower limit of the Mn content is 0.5% and the upper limit is 2.0%.

Si: 0.05 to 1.0% (preferably 0.1 to 0.8%)

Si is an element for improving strength, and is contained as necessary. However, if the Si content is small, the desired effect cannot be obtained, and if it is too large, the melting point decreases and the brazeability decreases. For these reasons, when Si is contained, the Si content is desirably within the above range. For the same reason, it is desirable that the lower limit is 0.1% and the upper limit is 0.8%. When Si is not positively contained, Si may be contained in an amount of less than 0.05% as an inevitable impurity.

Cu: 0.01 to 1.0% (preferably 0.01 to 0.8%)

Cu is an element for improving strength, and is contained as necessary. However, if the Cu content is small, the desired effect cannot be obtained, and if the Cu content is too large, the potential increases, the corrosion resistance deteriorates, and the melting point decreases. For these reasons, when Cu is contained, the Cu content is desirably within the above range. For the same reason, it is desirable that the lower limit is 0.01% and the upper limit is 0.8%.

Even if Cu is not positively contained, Cu may be contained as an inevitable impurity in an amount of less than 0.01%.

Fe: 0.1 to 0.7% (preferably 0.1 to 0.5%)

Fe is an element for improving strength, and is contained as necessary. However, if the Fe content is small, the desired effect cannot be obtained, and if the content is too large, a large intermetallic compound is generated at the time of casting, and the corrosion resistance is deteriorated. For these reasons, when Fe is contained, the content is desirably within the above range. For the same reason, it is desirable to set the lower limit to 0.1% and the upper limit to 0.5%. When Fe is not positively contained, 0.05% or less of Fe may be contained as an inevitable impurity.

[ sacrificial Material/core Material ]

If the Mn concentration of Si with respect to the core material is too high (including an amount increased by diffusion), Si precipitates on the grain boundaries, and if it is too low, Al — Mn second-phase particles precipitate on the grain boundaries to form a thin Mn layer on the grain boundaries, which leads to a decrease in corrosion resistance. Incidentally, the Al — Mn-based second phase particles or Mn/Si ratio can be adjusted by homogenization treatment or hot rolling, annealing temperature.

Mn/Si ratio in a region of 50 μm in the core depth direction from the sacrificial material/core interface after brazing: 0.5 to 5.0 (preferably 1.0 to 4.0)

By satisfying the above ratio, the corrosion resistance can be improved. If the ratio is too small, grain boundary corrosion occurs due to too much free Si, and if the ratio is too large, the strength is insufficient. For these reasons, it is desirable to set the content ratio within the above range. For the same reason, it is desirable that the lower limit of the content ratio is 1.0 and the upper limit is 4.0.

Potential difference of the highest layer in the sacrificial material and the lowest layer in the core material: 50 to 200mV (preferably 80 to 200mV)

By having the above potential difference, the corrosion resistance can be improved. If the potential difference is too small, the corrosion resistance is deteriorated, and if the potential difference is too large, the corrosion rate is increased. For these reasons, it is desirable to set the potential difference within the above range. For the same reason, it is desirable that the lower limit of the potential difference is 80mV and the upper limit of the potential difference is 200 mV.

Effects of the invention

As described above, according to the present invention, an aluminum alloy brazing sheet excellent in brazeability and corrosion resistance as a sacrificial material can be obtained.

Detailed Description

Hereinafter, embodiments of the present invention will be described.

An aluminum alloy for a core material and an aluminum alloy for a sacrificial material having the composition of the present invention were prepared. These alloys can be produced by a conventional method, and the production method is not particularly limited. For example, it can be manufactured by semi-continuous casting.

Al-Mn alloy is used as the aluminum alloy for the core material, and Al-Zn-Si alloy is used as the aluminum alloy for the sacrificial material.

The Al — Mn alloy for the core material preferably has the following composition: contains, in mass%, Mn: 0.3-2%, Si: 0.05-1%, Cu: 0.01 to 1.0%, Fe: 0.1 to 0.7%, and the balance of Al and unavoidable impurities. However, the composition of the Al-Mn based alloy is not limited to the above-mentioned ones.

The aluminum alloy for the sacrificial material can preferably be used as follows: contains Si: 2.0-5.0%, Zn: 3.0 to 5.0%, and if necessary, Mn: 0.1 to 1.0%, Fe: 0.1-0.7% of one or more than two.

After the aluminum alloy for core material or the aluminum alloy for sacrificial material is melted, homogenization treatment can be performed as necessary. The conditions for the homogenization treatment are not particularly limited, and for example, the core material may be homogenized at 400 to 600 ℃ for 4 to 16 hours, and the sacrificial material may be homogenized at 400 to 500 ℃ for 4 to 16 hours.

The aluminum alloy for the core material and the aluminum alloy for the sacrificial material are hot-rolled to produce a plate. Further, the plate material can be produced by continuous casting and rolling.

These sheet materials are clad at an appropriate cladding ratio in a state where a sacrificial material is disposed on one or both surfaces of a core material and stacked thereon. When a sacrificial material is disposed on one surface of the core member, a sacrificial material having another composition may be stacked on the other surface.

The cladding is usually performed by hot rolling. Then, by further performing cold rolling, an aluminum alloy brazing sheet having a desired thickness can be obtained.

In the present invention, the cladding ratio of the cladding material is not particularly limited, and for example, a sacrificial material thickness of 5 to 25%, a core material thickness of 75 to 95%, or the like is used.

The clad material is cold-rolled to a thickness of 0.15 to 0.80 mm. Further, intermediate annealing may be performed during cold rolling. The conditions of the intermediate annealing can be selected from the range of 200 to 380 ℃ and 1 to 6 hours.

After cold rolling, a final annealing can be performed. The final annealing is performed, for example, at 400 ℃ for 4 hours.

The obtained clad material can be used as a tube material for a heat exchanger, for example.

The tube material for the heat exchanger is brazed to a suitable member to be brazed, such as an inner fin.

The material, shape, and the like of the member to be brazed are not particularly limited as the present invention, and an appropriate aluminum material can be used.

As a result of the brazing, a heat exchanger tube can be obtained.

The heat treatment conditions for brazing are not particularly limited except for the temperature rise to 590 to 615 ℃, and may be, for example, the following conditions: heating at a heating rate of 1-10 minutes from 550 ℃ to the target temperature, keeping at the target temperature of 590-615 ℃ for 1-20 minutes, cooling to 300 ℃ at 50-100 ℃/min, and then air-cooling to room temperature.

Example 1

The sacrificial material and the aluminum alloy for the core material are cast by semi-continuous casting. The alloys shown in examples (the balance of Al and unavoidable impurities) were used as the sacrificial material and the aluminum alloy for the core material. Each alloy was homogenized for 10 hours under the temperature conditions shown in the examples.

Next, hot rolling was performed under predetermined conditions, and further cold rolling was performed until the sheet thickness became 0.5 mm. Then, annealing was performed for 3 hours under the temperature conditions described in examples to produce a quenched and tempered O plate material.

Production Process

Good homogenization treatment

After the slab casting, a homogenization treatment is performed for the purpose of removing inhomogeneous structures, for example, segregation.

By the high-temperature homogenization treatment, the additive elements supersaturated and dissolved in the matrix precipitate as intermetallic compounds during casting. Since the size and dispersion amount of the precipitated intermetallic compound have an influence on the temperature and time of the homogenization treatment, it is necessary to select heat treatment conditions according to the kind of the additive element.

Good hot rolling finishing temperature

In general, hot rolling is carried at a high temperature of around 500 ℃, but is coiled and cooled to room temperature after the rolling is finished. In this case, since the time for which the steel sheet is held at a temperature higher than the hot rolling completion temperature is changed, the precipitation behavior of the intermetallic compound is influenced.

Good brazing treatment

Brazing equivalent heat treatment was performed by the following method: heating the mixture from room temperature to 590-615 ℃ for about 20 minutes, keeping the mixture at 590-615 ℃ for 3-20 minutes, and then cooling the mixture from 590-615 ℃ to 300 ℃ at a cooling speed of 100 ℃/min.

Evaluation method

Distribution state of fine dispersed particles

The equivalent circle diameter and number density (. mu.m) of the dispersed particles were measured by scanning electron microscope (FE-SEM)²)。

The determination method comprises the following steps: a test material before brazing heat treatment was subjected to mechanical polishing and cross-sectional polishing (CP) processing to expose a plate profile (rolling direction parallel profile) and prepare a reagent, and photographs were taken at 10000 to 50000 times by FE-SEM. Photographs of 10 fields of view were taken, and the equivalent circle diameter and number density of the dispersed particles were measured by image analysis.

Good pore corrosion potential measurement

Pitting potential was determined by anodic polarization measurements. The reference electrode was Saturated Calomel Electrode (SCE), and the electrolyte was high purity N by blowing₂2.67% AlCl at 40 ℃ with sufficient degassing of the gas₃The solution was dissolved and measured at a scanning speed of 0.5 mV/s.

The measurement of the potentials of the eutectic brazing of the sacrificial material, the sacrificial material/core material interface layer and the core material was performed after the sample after the brazing heat treatment was etched and removed from the outermost surface of the sacrificial material with 5% NaO H (caustic soda) to have a predetermined plate thickness. Further, the potential measurement of the sacrificial material primary crystal brazing is performed after the sacrificial material eutectic brazing having the lowest potential is completely disappeared by anodic dissolution.

Good element diffusion state and Mn/Si ratio after brazing

The concentrations of Zn, Cu, Fe and Si in the direction of the thickness of the brazed sample were measured by EPMA line analysis. The Mn concentration was determined in each layer by EPMA semiquantitative analysis. Mn diffuses at a very low rate with respect to the Al matrix, and shows a substantially constant concentration in each layer regardless of the thickness direction, and therefore, it was measured at an arbitrary position in the thickness direction. Although only the count is analyzed in the online analysis, it is judged whether or not the diffusion state in each layer is uniform. From the results, the Mn/Si ratio in a region of 50 μm in the core depth direction from the sacrificial material/core interface was calculated. The concentration ratio is calculated as% by weight.

Regarding the Mn/Si ratio after brazing, it depends not only on the alloy composition but also largely on the heat treatment conditions. Generally, when a high-temperature heat treatment is performed, precipitation/growth of dispersed particles is promoted, and the solid solubility of Mn or Si is lowered. The Mn/Si ratio needs to be controlled by appropriately combining the homogenization treatment or hot rolling/annealing temperature conditions.

Good OY Water immersion test

The use of OY water (Cl-: 195ppm, SO 4) was performed^2-：60ppm，Cu²⁺：1ppm，Fe³⁺: 30ppm, balance pure water). The test conditions were evaluated up to 12 weeks with a one-day cycle of room temperature × 16h +88 ℃ × 8h (without stirring). The depth of etching was measured and the presence or absence of intergranular etching was confirmed. In the corrosion resistance evaluation in table 1, the evaluation results are expressed by Δ ∈ good ×.

[ evaluation standards ]

X produces significant grain boundary corrosion, Δ produces grain boundary corrosion and intracrystalline corrosion simultaneously, and good quality produces grain boundary corrosion (slight) and intracrystalline corrosion, and excellent only produces intracrystalline corrosion

Regarding the corrosion resistance, even if no intergranular corrosion occurs, the case where a through hole occurs within 12 weeks of the OY water immersion test was x.

Good degree of fluidity test in inverted T shape

To evaluate the brazeability, a test material having the upper surface as a sacrificial material was used in the horizontal material, and an inverted T-test was performed using the a3003 alloy in the vertical material. The evaluation results are shown as good quality x together with the brazing property evaluation in table 1.

[ evaluation standards ]

Good quality with no unbonded portion, x with unbonded portion. Further, a material which causes erosion of 150 μm or more in the core direction from the sacrificial material/core material interface is also referred to as "x".