CN111055558B

CN111055558B - Texture-strengthened composite aluminum strip for heat exchanger and preparation method thereof

Info

Publication number: CN111055558B
Application number: CN201811202365.7A
Authority: CN
Inventors: 张庆生; 马伟增; 李东飞
Original assignee: Granges AB
Current assignee: Granges AB
Priority date: 2018-10-16
Filing date: 2018-10-16
Publication date: 2022-02-01
Anticipated expiration: 2038-10-16
Also published as: CN111055558A

Abstract

The invention relates to a composite aluminium strip comprising a core alloy, wherein the core alloy comprises (a)0.3-1.2 wt% Si, 1.0-2.0 wt% Mn, 0.2-1.0 wt% Cu, 0.1-0.6 wt% Fe, (b) optionally one or more elements selected from: less than or equal to 0.5 weight percent of Mg, less than or equal to 0.3 weight percent of Ti, less than or equal to 0.3 weight percent of Zr, and the balance of aluminum and inevitable impurity elements; wherein the inevitable impurity elements are other elements selected from groups IVB, VB or VIB with a total content of less than or equal to 0.3 wt%, and/or other elements with a single element content of less than or equal to 0.05 wt% and a total content of less than or equal to 0.15 wt%; wherein the number of dispersed particle phases with the equivalent diameter of 0.02-less than 0.50 μm in the core alloy of the composite aluminum strip in a supplied state is 5 x 10⁹‑1×10¹²Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 7X 10⁶‑1×10⁹Per mm³. The invention also relates to a method for producing the composite aluminium strip and to the use thereof for heat exchangers.

Description

Texture-strengthened composite aluminum strip for heat exchanger and preparation method thereof

Technical Field

The present invention relates to a composite aluminum strip having high component P-oriented texture enhancement and high strength after brazing, suitable for use as a heat exchanger material. The invention also relates to a method for producing said composite aluminium strip and to the use thereof in heat exchangers.

Background

Because of the excellent properties of light specific gravity, corrosion resistance, good heat conduction, high strength, good brazing performance and the like, the multilayer composite aluminum strip or plate for brazing is widely applied to automobile heat exchange systems. With the increasing demand for weight reduction in the automotive industry, the weight reduction of heat exchangers is an inevitable trend. In order to meet the demand for weight reduction of heat exchangers, aluminum strips for manufacturing heat exchangers are also being increasingly thinned. In order for a heat exchanger after being lightened to have the same performance requirements as those before being lightened/thinned, and have good road test performance and fatigue resistance, the mechanical properties after welding of an aluminum plate strip which is continuously thinned are required to be continuously improved.

In the structure of the multilayer composite aluminum strip, the core material plays a supporting role and is also a main source of the strength of the material after welding. The water contact side has a lower corrosion potential than the core material and can serve as a sacrificial electrode protection core material. The Al-Si alloy of the brazing layer has a lower melting point and plays a brazing role in the brazing process.

As the main body of the multilayer composite aluminum strip, the core alloy determines the post-welding mechanical property of the whole aluminum strip material. The main alloying elements of the core alloy are Si, Mn, Cu, Mg and the like. The method for improving the strength of the core material is mainly realized by solid solution strengthening of alloying elements and particle strengthening of precipitated dispersion particle phase. Therefore, most of the prior art for enhancing the post-weld strength of composite aluminum plate materials is to add high contents of elements such as Si, Mn, Cu, etc. to enhance the post-weld performance of the material by higher solid solution strengthening and particle strengthening. However, the amount of alloying elements added cannot be increased indefinitely: the excessive Si and Cu content can greatly follow the melting point of the low core layer, so that the anti-corrosion capability of the core layer in the brazing process is obviously reduced; too high Mn (greater than 2.0 wt.%) will result in an alloy that is prone to coarse cast grain phases during casting, rendering the ingot unusable. Although the addition of Mg elements can achieve the purpose of improving the post-weld strength through solid solution strengthening and precipitation strengthening, the Mg content of the core alloy of the composite multilayer aluminum material for controlled gas shielded welding is generally limited to <0.3 wt% because Mg elements poison the flux, render the flux ineffective and affect the brazing quality. For some applications, the content of Mg is more strictly limited to <0.05 wt%, so most of the composite aluminum materials for heat exchangers cannot enhance the post-welding mechanical properties by adding Mg element to the core material.

Therefore, a new alloy strengthening technology and a production process different from solid solution strengthening and particle strengthening are needed to further improve and improve the post-weld strength of the composite aluminum strip.

Disclosure of Invention

In one aspect, the present invention relates to a composite aluminium strip comprising a core alloy, wherein the core alloy comprises (a) about 0.3-1.2 wt% Si, 1.0-2.0 wt% Mn, 0.2-1.0 wt% Cu, 0.1-0.6 wt% Fe, based on the core alloy, (b) optionally one or more elements selected from: about 0.5 wt.% or less Mg, 0.3 wt.% or less Ti, 0.3 wt.% or less Zr, and the balance aluminum and inevitable impurity elements; wherein the inevitable impurity elements are other elements selected from groups IVB, VB or VIB in a total content of about 0.3 wt% or less, and/or other elements in a single element content of about 0.05 wt% or less and in a total content of about 0.15 wt% or less; wherein the number of dispersed particle phases with an equivalent diameter in the range of 0.02 to less than 0.50 [ mu ] m in the core alloy in the supplied state of the composite aluminum strip is about 5 x 10⁹-1×10¹²Per mm³(ii) a And the number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00 mu m is about 7X 10⁶-1×10⁹Per mm³。

In one embodiment, the composite aluminium strip of the present invention comprises about 0.5-1.0 wt.% Si, and/or about 1.3-1.8 wt.% Mn, and/or about 0.3-0.8 wt.% Cu, based on the core alloy.

In another embodiment, the composite aluminum strip of the present invention has a core alloy with Mn in solid solution in aluminum in an amount of about 0.02 to about 0.10 wt%.

In one embodiment, the composite aluminum strip of the present invention further comprises a braze layer alloy.

In one embodiment, the composite aluminum strip of the present invention includes about 4 to 12 wt.% Si, less than or equal to 0.6 wt.% Fe, less than or equal to 1.0 wt.% Mn, less than or equal to 1.0 wt.% Cu, less than or equal to 1.0 wt.% Zn, the balance being aluminum and unavoidable impurity elements; wherein the inevitable impurity elements are other elements selected from groups IVB, VB or VIB in a total content of about 0.3 wt.% or less and/or other elements in a single element content of about 0.05 wt.% or less and in a total content of about 0.15 wt.% or less.

In yet another embodiment, the composite aluminum strip of the present invention optionally comprises a water-contacting side alloy, wherein the water-contacting side alloy comprises about 0.5 to 5.5 wt.% Zn, 0 to 1.5 wt.% Si, 0 to 2.0 wt.% Mn, 0.6 wt.% or less Fe, 0 to 1.0 wt.% Mg, the balance aluminum and inevitable impurity elements, based on the water-contacting side alloy; wherein the inevitable impurity elements are other elements selected from groups IVB, VB or VIB in a total content of about 0.3 wt.% or less and/or other elements in a single element content of about 0.05 wt.% or less and in a total content of about 0.15 wt.% or less.

In one embodiment, the composite aluminum strip of the present invention is clad with a brazing layer alloy on one or both sides of the core alloy.

In one embodiment, the total thickness of the composite aluminum strip of the present invention is about 0.10 to 1.00 mm.

In another aspect, the invention relates to a method of making the composite aluminum strip of the invention comprising

a) Casting ingots of the core alloy, the braze layer alloy, and optionally the water-contacting side alloy separately,

b) homogenizing and heat-treating the core material alloy,

c) sawing, milling the surface and combining the core alloy, brazing layer alloy and the optionally present thick plate pieces of the alloy on the water contact side,

d) hot rolling is carried out, and the hot rolled steel is subjected to hot rolling,

e) cold rolling the mixture to obtain the finished product,

f) performing intermediate heat treatment on the mixture,

g) cold-rolling the mixture into a belt,

h) annealing the finished product;

wherein the temperature of the homogenization heat treatment in the step b) is about 450 ℃ and 550 ℃, and the time of the homogenization heat treatment is about 5 to 10 hours;

the temperature of the intermediate heat treatment in step f) is about 200 ℃ to 400 ℃, and the time of the intermediate heat treatment is about 1 to 5 hours.

In one embodiment, the instant inventionIn the inventive method for producing a composite aluminium strip, the number of dispersed particle phases having an equivalent diameter in the range of 0.02 to less than 0.50 μm in the core alloy after step b) is about 1 x 10⁸-1×10¹⁰Per mm³(ii) a And the number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00 mu m is about 2X 10⁵-1×10⁷Per mm³。

In another embodiment, in the method of producing a composite aluminium strip according to the invention, the number of dispersed particulate phases having an equivalent diameter in the range of 0.02 to less than 0.50 μm in the core alloy of the composite aluminium strip after step f) is about 5 x 10⁹-1×10¹²Per mm³(ii) a And the number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00 mu m is about 7X 10⁶-1×10⁹Per mm³。

In yet another embodiment, the method of making a composite aluminum strip of the present invention, the Mn element content of the composite aluminum strip core alloy in solid solution with aluminum after step f) is about 0.02 to 0.10 wt.%.

In yet another aspect, the present invention relates to a core alloy, wherein the core alloy comprises (a) about 0.3-1.2 wt.% Si, 1.0-2.0 wt.% Mn, 0.2-1.0 wt.% Cu, 0.1-0.6 wt.% Fe, (b) optionally one or more elements selected from: about 0.5 wt.% or less Mg, 0.3 wt.% or less Ti, 0.3 wt.% or less Zr, and the balance aluminum and inevitable impurity elements; wherein the inevitable impurity elements are other elements selected from groups IVB, VB or VIB in a total content of about 0.3 wt% or less, and/or other elements in a single element content of about 0.05 wt% or less and in a total content of about 0.15 wt% or less; wherein the number of dispersed particle phases in the core alloy having an equivalent diameter in the range of 0.02 to less than 0.50 μm is about 5 x 10⁹-1×10¹²Per mm³(ii) a And the number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00 mu m is about 7X 10⁶-1×10⁹Per mm³。

In one embodiment, the content of Mn element in the core alloy of the present invention in the aluminum solid solution is about 0.02 to 0.10 wt%.

In one embodiment, the P-oriented texture after brazing of the composite aluminium strip of the invention or the composite aluminium strip produced by the method of the invention or the core alloy of the invention is above about 45%.

In a further aspect, the invention relates to the use of the composite aluminium strip according to the invention or the composite aluminium strip prepared by the method according to the invention or the core alloy according to the invention in a heat exchanger.

Drawings

FIGS. 1a-1 c: the structure of the composite aluminum strip of the embodiment of the invention is shown schematically (A: core material; B: brazing layer; C: water contact side).

FIG. 2: scanning electron micrograph of core alloy of sample of example 1 (dispersed particle phase as white bright spot)

FIG. 3: post weld grain orientation profile of the composite aluminum strip of example 1.

FIG. 4: post weld grain orientation profile of the composite aluminum strip of example 2.

FIG. 5: post weld grain orientation profile of the composite aluminum strip of comparative example 1.

FIG. 6: post weld grain orientation profile of the composite aluminum strip of comparative example 2.

Detailed Description

General definitions and terms

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In case of conflict, the present application will control.

All percentages, parts, ratios, etc. herein are by weight unless otherwise indicated.

When an amount, concentration, or other value or parameter is expressed in terms of a range, preferred range, or upper preferable numerical value and lower preferable numerical value, it is understood that any range defined by any pair of upper range limits or preferred numerical values in combination with any lower range limits or preferred numerical values is specifically disclosed, regardless of whether the range is specifically disclosed. Unless otherwise indicated, numerical ranges set forth herein are intended to include the endpoints of the ranges, and all integers and fractions within the ranges. For example, "1-8" encompasses 1, 2, 3, 4, 5, 6, 7, 8, as well as any subrange consisting of any two values therein, e.g., 2-6, 3-5.

The expressions "comprising" or similar expressions "including", "containing" and "having" and the like which are synonymous are open-ended and do not exclude additional, unrecited elements, steps or components. The expression "consisting of …" excludes any element, step or ingredient not specified. The expression "consisting essentially of …" means that the scope is limited to the specified elements, steps or components, plus optional elements, steps or components that do not materially affect the basic and novel characteristics of the claimed subject matter. It is to be understood that the expression "comprising" covers the expressions "consisting essentially of …" and "consisting of …".

The term "about" as used herein may allow for a degree of variation in the value or range, such as within the stated value or range of the stated limit and including within 10%, within 5% or within 1% of the exact value or range.

The terms "optionally" or "optionally" as used herein mean that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not. For example, as used herein, composite aluminum strip optionally includes a water contact side alloy, meaning that the composite aluminum strip may or may not include a water contact side alloy.

The term "one or more" as used herein means 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or more.

The term "composite aluminium strip" as used herein refers to a material which is a composite of a core alloy, a brazing layer alloy and optionally a water contact side alloy, and may also be referred to as composite aluminium foil, composite aluminium strip, composite sheet material.

The term "as-delivered" as used herein means the final processed state of the alloy, e.g., as-delivered final plastic deformation state or final heat treated state. In this context, in particular the state of the composite aluminium strip before brazing after the preparation is complete.

As used herein, the term "inevitable impurity elements" refers to elements that are not actively added during the preparation of the aluminum alloy, and are difficult to avoid entering the alloy. In this context, unavoidable impurity elements are other elements from groups IVB, VB or VIB in a total content of ≦ 0.3 wt.%, and/or other elements in a single element content of ≦ 0.05 wt.% and in a total content of ≦ 0.15 wt.%. Wherein "other elements" means that the elements already indicated are not included in the corresponding alloys. For example, "other elements selected from group IVB, VB or VIB" in the core alloy means the remaining elements of group IVB, VB or VIB in addition to Ti, Zr already indicated. Similarly, the "other elements" in "other elements having a single element content of 0.05 wt.% or less and a total content of 0.15 wt.% or less" in the core alloy means the remaining elements other than Si, Mn, Cu, Fe, Mg, Ti, Zr and "other elements from group IVB, VB or VIB" (if present) in a total content of 0.3 wt.% or less, as already indicated. Elements from group IVB, VB or VIB such as Ti, Zr, Cr, etc. In one embodiment, the element selected from group IVB, VB or VIB forms a dispersoid or fine particulate phase with Al in the alloy, such as Al₃Zr. Such as P, B, Ca, etc.

The term "dispersed particulate phase" as used herein means that elements of Si, Mn, Cu, etc. dissolved in solid solution precipitate from solid solution during thermo-mechanical processing to form a finely sized, widely distributed particulate phase, which is different from the cast particulate phase. In this context, the dispersed particle phase mainly refers to the particle phase of Al-Mn (Cu) -Si. The size and distribution of these particulate phases can be measured by observation with a scanning electron microscope. The dispersed particulate phase has an equivalent diameter of approximately 0.02 to 1.00. mu.m, predominantly 0.02 to less than 0.5. mu.m. Herein, the calculated number of particle equivalent diameters in the core alloy is the number of particle equivalent diameters of the dispersed particle phase in the core alloy.

As used herein, the term "cast particulate phase" refers to the larger sized particulate phase formed during solidification of an ingot. The cast particle phase is substantially unchanged during subsequent thermomechanical processing.

The term "solid solution" as used herein refers to an alloy phase in which solute atoms dissolve into the solvent lattice while still maintaining the solvent type. In this context, solid solution mainly refers to a supersaturated aluminum solid solution in which alloying elements such as Si, Cu, Mn, etc. are "solidified" in an aluminum phase in a short time to precipitate from the solidified aluminum phase due to a high cooling rate during casting. Supersaturated solid solutions during subsequent thermomechanical processing solute atoms such as Si, Cu, Mn will precipitate out of solid solution, forming a dispersed particulate phase.

The term "solid solubility" as used herein refers to the maximum content of alloying elements such as Si, Cu, Mn, etc. in the aluminum solid solution. Solid solubility is closely related to temperature. Because the cooling speed of the cast ingot is high in the casting process, the solid solution formed at high temperature is rapidly cooled to room temperature, and excessive alloying elements are retained in the solid solution, so that a supersaturated solid solution is obtained. The supersaturated solid solution, when heated, precipitates a portion of the alloying elements that exceed the solid solubility from the solid solution, thereby obtaining a dispersoid phase. The solid solubility of the Mn element in the aluminum solid solution may also be referred to as the content of the Mn element in the aluminum solid solution. It can be calculated indirectly by measuring the resistance and the thermoelectric potential and then using the relationship between the solid solubility of Mn and the resistance and the thermoelectric potential. For example, herein, the content of Mn element in the core alloy in the aluminum solid solution is measured using a combination of the resistance method and the thermoelectric force method. On the one hand, the resistance of AA3 xxx-series aluminum alloys is clearly related to the solid solubility of Mn element in aluminum solid solution, i.e., the precipitation and solid solution of Mn changes the resistance of the material. On the other hand, the thermoelectric potential of the material is also affected by the solid solubility of Mn element in solid solution. Based on the two theories, the solid solubility of Mn element in AA3xxx series aluminum alloy is calculated by measuring the resistance and the thermoelectric potential of the material and utilizing a coupled mathematical model.

The term "P-oriented texture" as used herein refers to a P-oriented (011 <111>) crystal orientation of a large portion of recrystallized grains formed after brazing of the composite aluminum strip, and the preferred orientation of the grains is referred to as P-oriented texture. Texture can be measured by Electron Back Scattering Diffraction (EBSD). The P-oriented texture of the composite aluminum strip of the invention is about 45% or more. In the process of brazing the supplied material to obtain a P-oriented texture, the brazing is performed in a manner well known to those skilled in the art. For example, the composite aluminum strip is warmed from room temperature to about 600 ℃ over about 20 minutes and held for about 3 minutes.

The term "high fraction" as used herein means that the P-oriented texture has the highest fraction of all orientations (i.e., random orientation + recrystallized orientation).

The term "AA 3xxx series" designation as used herein refers to the aluminum association's common alloy designation.

As used herein, the term "room temperature" means about 20-30 deg.C, preferably 25 deg.C.

The term "rolling orientation" as used herein refers to: during the rolling deformation of the aluminum alloy, the crystals and the slip planes thereof slip and rotate, so that the orientation of crystal grains in the polycrystal is ordered to a certain degree, and the preferred orientation of the crystal grains directly generated in the deformed metal due to the deformation is called as rolling orientation. The aluminum alloy for the heat exchanger is rolled aluminum alloy. As shown in table 1, the aluminum alloy rolling orientation includes three types: copper orientation, bronze orientation, and S orientation. The composite aluminum strip for heat exchangers described herein is in a rolled orientation as it is supplied.

TABLE 1 crystallographic orientation common in aluminum alloys

As used herein, the term "recrystallized orientation" means that the aluminum strip having a rolling orientation recrystallizes when subjected to high temperature brazing, forms new recrystallized grains, and has a new crystallographic orientation, referred to as a recrystallized orientation. The aluminum alloy recrystallization orientation includes: cubic orientation, R orientation, P orientation, and Q orientation (see table 1).

The term "randomly oriented" as used herein means that the composite aluminum strip for heat exchangers is a recrystallized polycrystalline body after brazing, and if each grain has a crystallographic orientation different from that of the adjacent grains, the orientation of all grains is randomly distributed as a whole.

The term "preferred orientation or texture" as used herein means that the grains of the above-described polycrystalline body are arranged in some particular orientation to the extent that the polycrystalline material exhibits a crystallographically preferred orientation or texture. The mechanical properties of the polycrystalline aluminum strip with preferred orientation or texture show strong anisotropy, namely the strength of the material in a certain direction is obviously enhanced. The composite aluminum strip for the heat exchanger needs to be manufactured into pipes with different shapes in the using process through high-frequency welding or roll forming and the like, then the pipes are assembled with the main plate, the side plate and the fins together, and the final heat exchanger is manufactured through controlled gas shielded brazing. The strength of the composite aluminium strip after brazing in the rolling direction plays an important role in the overall strength of the heat exchanger. The texture causes the anisotropic material characteristic of the material, and if the composite aluminum strip is enabled to have a strong texture of certain crystallographic recrystallization orientation after brazing, the mechanical property of the aluminum strip in the rolling direction can be effectively enhanced, thereby achieving the purpose of enhancing the heat exchanger and providing further space for material thinning. Therefore, texture strengthening is a very effective technical means for reinforcing the composite aluminum strip for heat exchangers, which is different from solid solution strengthening and particle strengthening.

The term "equivalent diameter" as used herein refers to the diameter of an irregularly shaped particle when converted to a circular particle having the same area as the irregular shaped particle, and the equivalent diameter of a dispersed particle phase may also be referred to herein as the size of the dispersed particle phase.

The materials, methods, and examples herein are illustrative and, unless otherwise specified, are not to be construed as limiting.

The composite aluminum strip and the method of making the composite aluminum strip are described in detail below.

The invention relates to a composite aluminium strip comprising a core alloy. In one embodiment, the composite aluminum strip has a dispersed particulate phase having an equivalent diameter in the range of 0.02 to less than 0.50 μm in the core alloy in the as-supplied state in an amount of about 5 x 10⁹-1×10¹²Per mm³(ii) a And the number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is about 7X 10⁶-1×10⁹Per mm³。

Core alloy

In the composite aluminum strip of the present invention, the core alloy contains

(a)0.3 to 1.2% by weight of Si,

1.0 to 2.0 wt.% of Mn,

0.2 to 1.0 wt.% of Cu,

0.1-0.6 wt.% Fe, and

(b) optionally one or more elements selected from:

less than or equal to 0.5 weight percent of Mg,

Less than or equal to 0.3 weight percent of Ti,

Zr of less than or equal to 0.3 weight percent,

the balance of aluminum and inevitable impurity elements;

wherein the inevitable impurity elements are other elements selected from groups IVB, VB or VIB with a total content of less than or equal to 0.3 wt%, and/or other elements with a single element content of less than or equal to 0.05 wt% and a total content of less than or equal to 0.15 wt%.

The elements Si and Mn play a key role in preparing the alloy with the strengthened texture. In the core material, Si promotes the precipitation of Mn from a solid solution to obtain an AlMnSi high-density dispersed granular phase; meanwhile, the aim of controlling the content of Mn in the aluminum solid solution to be kept in a proper range is achieved through the precipitation of AlMnSi particles. The inventor finds that the solid solubility and high-density AlMnSi dispersed phase of Mn element in aluminum solid solution play an important role in the preferred orientation nucleation and preferred orientation growth of P crystal grains during the recrystallization of the aluminum strip.

Based on the core material alloy of the present invention, if the Si content is less than about 0.3 wt%, the solid solubility of Mn is not effectively reduced, and the amount of precipitated dispersed particle phase is small, thereby being disadvantageous to the preferential nucleation and growth of P crystal grains. The Si content exceeding about 1.2 wt% may cause the dissolved Mn element to be entirely precipitated from the aluminum solid solution. In addition, the melting point of the core material is greatly reduced by excessively high Si, so that the anti-corrosion capability of the aluminum strip is greatly reduced, and the brazing performance of the material is influenced. The amount of Si in the core alloy is about 0.3-1.2 wt.%, preferably about 0.5-1.0 wt.%, more preferably about 0.55-0.90 wt.%, even more preferably 0.60-0.90 wt.%, e.g. about 0.8, 0.6 wt.%, based on the core alloy of the present invention.

Mn is a main element for solid solution strengthening and particle strengthening of AA3 xxx-series aluminum alloys. The amount of dispersed particle phase precipitation depends on the precipitation of Mn from solid solution. At Mn levels below about 1.0 wt.%, both the solid solution strengthening and the grain strengthening are significantly reduced, and the post-weld strength of the material is reduced; meanwhile, the number of particles promoting the preferential nucleation and growth of the P-oriented crystal grains is low, and most of Mn is precipitated from the solid solution due to the Si element in the alloy, so that the formation of the P-oriented texture is not facilitated. When the Mn content exceeds about 2.0 wt%, coarse casting compound phases may appear in the cast structure, making the ingot unusable. The content of Mn in the core alloy is about 1.0-2.0 wt.%, preferably about 1.3-1.8 wt.%, for example about 1.5, 1.4 wt.%, based on the core alloy of the present invention.

Cu has the functions of improving the mechanical property after welding and adjusting the corrosion potential of the core alloy. Based on the core material alloy of the invention, when the content of Cu is less than about 0.2 wt%, the strengthening effect is weaker, and the corrosion potential of the core material alloy is too low, which is not favorable for corrosion protection of the pipe in a heat exchanger. When the Cu content exceeds about 1.0 wt%, the corrosion potential of the core alloy becomes too high, and the material is more likely to undergo intergranular corrosion. In addition, too high Cu content increases the risk of casting cracking of the cast ingot, and is not beneficial to large-scale industrial production. Based on the core alloy of the present invention, the content of Cu is about 0.2-1.0 wt.%, preferably about 0.3-0.8 wt.%, for example about 0.55 wt.%.

The Fe element is present in the aluminum ingot in the form of a casting compound phase. These cast large grain phases are the primary nucleation cores, i.e., grain-induced nucleation cores, of the P-oriented grains upon recrystallization of the rolled aluminum alloy. When the Fe content is less than about 0.1 wt%, the grain-induced nucleation cores are too small to be favorable for P-oriented grain nucleation. Too high Fe will result in the formation of coarse casting compound phases and the ingot will be unusable. The amount of Fe is about 0.1-0.6 wt%, preferably about 0.15-0.4 wt%, for example about 0.25 wt%, based on the core alloy of the present invention.

Mg element is a solid solution strengthening and age strengthening alloy element. Mg element can be added or not added according to actual requirements. Too high Mg element will poison the flux and reduce the brazing quality. The Mg content is controlled to be less than or equal to about 0.5 wt%, preferably less than or equal to about 0.3 wt%, for example, about 0.005 to 0.3 wt%, such as about 0.02, 0.2 wt%.

Ti may act as a grain refiner. Too high a Ti content will lead to coarse casting compounds in the ingot, which will render the ingot unusable. The Ti content is controlled to be less than or equal to about 0.3 wt%, for example, about 0.02 to 0.20 wt%, such as about 0.15, 0.13, 0.02 wt%.

Zr can form a fine dispersed particle phase, has the same action with AlMnSi dispersed particles, and is beneficial to the nucleation and growth of P-oriented grains. However, too high Zr element will cause the ingot to have coarse casting compound, resulting in the ingot being unusable. The Zr content is controlled to be about 0.3 wt.% or less, for example about 0.02 to 0.2 wt.%, such as about 0.12, 0.02 wt.%.

In one embodiment, the core alloy does not contain Zn element to avoid lowering the potential of the core alloy, resulting in accelerated corrosion of the core alloy. In another embodiment, the content of Zn element is <0.1 wt%, for example about 0.02 wt%.

Brazing layer alloy and water contact side alloy

In the composite aluminum strip of the present invention, a brazing layer alloy is further contained.

Based on the brazing layer alloy, the brazing layer alloy comprises

4-12% by weight of Si,

Fe of less than or equal to 0.6 weight percent,

Mn of not more than 1.0 wt%,

Cu of not more than 1.0 wt%,

Less than or equal to 1.0 weight percent of Zn,

the balance of aluminum and inevitable impurity elements;

The brazing layer alloy of the present invention is an Al — Si alloy. The brazing layer has an elemental composition such that the composite aluminum strip can be brazed without adversely affecting the core alloy.

In a preferred embodiment, the Si content is about 5.0 to 10.0 wt%, e.g., about 10.0, 7.5 wt%. In another preferred embodiment, the Fe is present in an amount of about 0.1 to 0.45 wt%, for example about 0.15 wt%.

The contents of Mn, Cu and Zn can be selected according to the requirements of practical application. In one embodiment, Mn, Cu, Zn need not be added intentionally, so that the content of Mn, Cu, Zn in the braze layer alloy is about <0.1 wt.%, preferably about <0.05 wt.%, for example about 0.02 wt.%, respectively.

In one embodiment, the braze layer alloy is AA 4343.

In the composite aluminum strip of the present invention, a water contact side alloy is optionally further contained. Based on the water-contact side alloy, the water-contact side alloy comprises

0.5 to 5.5 wt.% of Zn,

0 to 1.5% by weight of Si,

0 to 2.0 wt.% of Mn,

Fe of less than or equal to 0.6 weight percent,

0-1.0 wt.% of Mg,

the balance of aluminum and inevitable impurity elements;

The water contact side alloy of the present invention is a Zn-containing AA3 xxx-series alloy. Zn has a sacrificial anode effect. By diffusion of the Zn element during brazing, a corrosion potential gradient is formed, slowing down the risk of corrosion from the anti-icing liquid. The Zn content is about 0.5 to 5.5 wt%, preferably about 1.0 to 4.0 wt%, for example about 2.5 wt%, based on the water contact side alloy of the present invention.

The recrystallization temperature of the water-contact side alloy with low Mn content or no Mn will be low, it will be possible to completely recrystallize after annealing the finished product, and its P-oriented texture will also be low. In order to ensure that the water contact side alloy has high P orientation texture after brazing, the contents of Si and Mn also need to be close to the contents of Si and Mn of the core alloy, so that the water contact side alloy is ensured to have recrystallization temperature which is relatively close to that of the core alloy, and simultaneously, the water contact side alloy can be ensured to have enough dispersed particle phase and a certain amount of Mn solid solubility before brazing, and the preferential growth of P crystal grains during recrystallization is promoted. The Mn content is about 0 to 2.0 wt.%, preferably about 1.3 to 1.8 wt.%, for example about 1.4 wt.%, based on the water-contact side alloy of the present invention. Based on the water contact side alloy of the present invention, the content of Si is about 0 to 1.5 wt%, preferably about 0.5 to 0.8 wt%, for example 0.65 wt%.

A certain amount of Mg can be added to the water contact side according to actual requirements. In one embodiment, no Mg is intentionally added, so that the amount of Mg in the braze layer alloy is about 0-0.1 wt.%, preferably about 0-0.05 wt.%, for example about 0.02 wt.%.

In a preferred embodiment, the Fe is present in an amount of about 0.10 to 0.45 wt%, for example about 0.26 wt%.

Composite aluminium strip

The invention relates to a composite aluminium strip comprising a core alloy. The composite aluminium strip may also comprise a braze layer alloy and optionally a water-contact side alloy. In one embodiment, the composite aluminum strip has a dispersed particulate phase having an equivalent diameter in the range of 0.02 to less than 0.50 μm in the core alloy in the as-supplied state in an amount of about 5 x 10⁹-1×10¹²Per mm³Preferably about 1X 10¹⁰-8×10¹¹Per mm³E.g. about 3X 10¹⁰Per mm³、5×10¹⁰Per mm³. In another embodiment, the dispersed particulate phase has an equivalent diameter in the range of 0.50 to 1.00. mu.m, and the amount is about 7X 10⁶-1×10⁹Per mm³Preferably about 1X 10⁷-6×10⁸Per mm³E.g. is about1×10⁷Per mm³、2×10⁷Per mm³. In yet another embodiment, the Mn element of the core alloy in solid solution in aluminum is present in an amount of about 0.02 to about 0.10 wt.%, preferably about 0.03 to about 0.08 wt.%, of the composite aluminum strip of the present invention in the as-supplied state.

The composite aluminum strip is a two-layer or three-layer composite material, and preferably a three-layer composite material.

In one embodiment, the brazing layer alloy is clad on one or both sides of the core alloy.

In another embodiment, a water contact side alloy is clad on one face of the core alloy.

In yet another embodiment, the composite aluminum strip does not include a water contact side alloy.

In yet another embodiment, the composite aluminum strip of the present invention has the structure: a brazing layer alloy B is coated on one surface of the core material alloy a, and a water contact side alloy C is coated on the other surface of the core material alloy a away from the brazing layer alloy B, as shown in fig. 1 a.

In another embodiment, the composite aluminum strip of the present invention has the structure: the two opposite surfaces of the core alloy a are coated with the brazing layer alloy B, respectively, and are not coated with the water contact side alloy, as shown in fig. 1B.

In yet another embodiment, the composite aluminum strip of the present invention has the structure: one surface of the core alloy a was coated with a brazing layer alloy B, and the composite aluminum strip did not contain a water contact side alloy, as shown in fig. 1 c.

The total thickness of the composite aluminum strip of the present invention is about 0.1 to 1.0mm, preferably about 0.15 to 0.45 mm. The high performance is kept and the thinning requirement is also met.

The thickness of the single layer as a percentage of the total thickness of the composite aluminium strip is expressed as the composite ratio. The recombination ratio generally refers to the recombination ratio on one side. The composition ratio of the brazing layer alloy, and optionally the composition ratio of the water contact side alloy, in the composite aluminium strip of the invention are not particularly limited, but should be such that a composite aluminium strip of the target thickness is obtainable.

In one embodiment, the composite ratio of the braze layer alloy is about 5-15%, for example about 10%, based on the total thickness of the composite aluminum strip of the invention.

In another embodiment, the composite ratio of the water-contact side alloy is about 5 to 15%, for example about 15%, based on the total thickness of the composite aluminum strip of the invention.

In yet another embodiment, the composite ratio of the core alloy is about 70-90%, such as about 75%, 80%, based on the total thickness of the composite aluminium strip of the invention.

Preparation method of composite aluminum strip

The invention also relates to a method for producing the composite aluminium strip according to the invention, comprising

a) Casting ingots of the core alloy, the braze layer alloy, and optionally the water-contacting side alloy separately;

b) homogenizing and heat-treating the core material alloy;

c) sawing, milling the surface and compounding the core alloy, the brazing layer alloy and the thick plate sheet of the alloy on the water contact side;

d) hot rolling;

e) cold rolling;

f) intermediate heat treatment;

g) cold rolling into a belt;

h) annealing the finished product;

a) Separately casting ingots of core alloy, brazing layer alloy and optionally water-contacting side alloy

Ingots of core alloy, brazing layer alloy and optionally water-contact side alloy are produced separately by a water-cooled semi-continuous casting process, which for example comprises the following steps: adding an industrial pure aluminum ingot into a smelting furnace for melting at the smelting temperature of about 730-760 ℃, slagging off, sampling and analyzing, adding alloy elements according to the components of the cast ingot of the core layer alloy, the brazing layer alloy and the optional water contact side alloy, standing, stirring, refining, slagging off, adjusting the components, pouring into a standing furnace, stirring, refining, slagging off again, performing online modification treatment, degassing, filtering, and feeding into a casting machine for casting to form the cast ingot.

b) Homogenizing heat treatment of the core alloy

The inventors of the present invention have found that a composite aluminum strip having a strong P orientation has a higher strength in the rolling direction after brazing. Therefore, on the basis of keeping the solid solution strengthening and the particle strengthening of the aluminum strip material, the texture strengthening is an effective means for further improving the strength of the alloy after brazing.

The recrystallization texture of the composite aluminum strip is closely related to the chemical composition of the core alloy and the production history of the aluminum strip. The preferential formation of P-oriented grains depends on the precipitation of dispersed particle phases and the solid solubility of the Mn element in the aluminum matrix. The high density of dispersed particulate phase contributes to the formation of P-oriented texture, which requires Mn to precipitate from solid solution; the solid solubility of Mn in solid solution before recrystallization also strongly affects the nucleation of P-oriented grains, so that the core material needs to retain a certain amount of Mn element in aluminum solid solution before recrystallization. If it is desired that the composite aluminum strip have a strong P-oriented texture after brazing, the precipitation and solid solution of Mn element in the core material need to be precisely controlled.

The inventors of the present invention have further investigated and found that by subjecting the core alloy in step b) to a homogenization heat treatment and subjecting the aluminium strip in step f) to an intermediate heat treatment, it is helpful to produce a composite aluminium strip having a strong P-oriented texture after brazing, e.g. having a P-oriented texture composition of about 45% or more, such as about 55%, 48%.

The homogenization heat treatment refers to the heat preservation treatment of the alloy in a homogenization furnace. Too high a temperature will cause coarsening of the dispersed particle phase, while too low a temperature will cause the Mn content in solid solution to be difficult to control effectively within the desired range. In one embodiment, the temperature of the homogenization heat treatment of the core alloy in step b) is about 450-.

The homogenizing heat treatment apparatus is a heat treatment apparatus conventionally used in the art, and is, for example, a heat treatment furnace. The time of the homogenization heat treatment will be adjusted based on the particular combination of alloying elements used and the homogenization heat treatment equipment used. The time for the homogenization heat treatment of the core alloy in step b) is about 5 to 10 hours, preferably about 5 to 8 hours, for example about 8 hours.

The control of the temperature and time of the homogenization heat treatment in step b) helps to control the number and equivalent diameter of the dispersed particle phases and the content of Mn in the aluminum solid solution within desired ranges. In one embodiment, after this step, the number of dispersed particles having an equivalent diameter in the range of 0.02 to less than 0.50 μm is about 1X 10⁸-1×10¹⁰Per mm³Preferably about 5X 10⁸-1×10⁹Per mm³E.g. about 5X 10⁸Per mm³、8×10⁸Per mm³. In another embodiment, the dispersed particulate phase has an equivalent diameter in the range of 0.50 to 1.00. mu.m, by number of about 2X 10⁵-1×10⁷Per mm³Preferably about 5X 10⁵-5×10⁶Per mm³E.g. about 1X 10⁶Per mm³、3×10⁶Per mm³。

Typically, the braze layer alloy and the water contact side alloy are optionally homogenized. In one embodiment, neither the braze layer alloy nor the water contact side alloy requires homogenization treatment.

c) Sawing, milling and combining the core alloy, brazing layer alloy and optionally the thick plate pieces of the alloy on the water contact side

Saw cutting

The bottom of the core alloy, brazing layer alloy and optionally the water-contacting side alloy ingot prepared as above is sawn off, for example 200 and 500 mm.

Milling surface

The sawn core alloy, brazing layer alloy and optionally the water-contact side alloy ingot are milled off on both sides, for example, by 5 to 20mm each.

Compounding

In one embodiment, a thickness of brazing layer alloy is clad on both sides of the core alloy.

In another embodiment, a brazing layer alloy is compounded to a certain thickness on one side of the core alloy, and a water contact side alloy is compounded to a certain thickness on the other side of the core alloy opposite to the core alloy.

In one embodiment, the composite ratio of the braze layer alloy is about 5-15%, such as about 10%, based on the total thickness of the composite aluminum strip.

In another embodiment, the composite ratio of the alloy on the water-contacting side (if present) is from about 5 to 15%, such as about 15%, based on the total thickness of the composite aluminum strip.

And compounding the core alloy, the brazing layer alloy and the optional water contact side alloy, and then performing head-to-tail welding by using an argon arc welding machine.

d) Hot rolling

The term "hot rolling" in step d) means rolling the composite alloy on a hot rolling mill to a strip having a thickness of about 3-5mm, for example about 3.5 mm. The temperature and time of hot rolling are not particularly limited, and those skilled in the art can select the temperature and time in combination with the actual circumstances as long as the objective product of the present invention can be obtained. For example, the hot rolling temperature may be about 450-.

e) Cold rolling

The term "cold rolling" in step e) means that the cooled strip is cold rolled in several passes in a cold rolling mill to a thickness of about 1-2mm, e.g. 1.5 mm. The temperature and time of the cold rolling are not particularly limited, and those skilled in the art can select the temperature and time in combination with the actual circumstances as long as the objective product of the present invention can be obtained. For example, cold rolling may be performed at room temperature.

f) Intermediate heat treatment

There is one intermediate heat treatment during the cold rolling.

The control of the temperature and time of the intermediate heat treatment of step f) further contributes to the control of the amount and equivalent diameter of the dispersed particle phase in the treated aluminium strip and the content of Mn in solid solution in the aluminium within the desired ranges. Too high an intermediate heat treatment temperature tends to cause recrystallization of the core material. Too low an intermediate heat treatment temperature will result in less precipitation of dispersed particulate phase. In one embodiment, the temperature of the intermediate heat treatment in step f) is about 200-.

The intermediate heat treatment apparatus is a heat treatment apparatus conventionally used in the art, and is, for example, a heat treatment furnace. The time of the heat treatment will be adjusted based on the particular combination of alloying elements used and the heat treatment equipment used. The time for the intermediate heat treatment in step f) (otherwise known as the incubation time) is about 1 to 5 hours, preferably about 2 to 3 hours, for example about 2 hours.

In one embodiment, the number of dispersed particle phases in the core alloy of the composite aluminium strip after step f) having an equivalent diameter of dispersed particle phases in the range of 0.02 to less than 0.50 μm is about 5 x 10⁹-1×10¹²Per mm³Preferably about 1X 10¹⁰-8×10¹¹Per mm³E.g. about 3X 10¹⁰Per mm³、5×10¹⁰Per mm³. In another embodiment, the dispersed particulate phase has an equivalent diameter in the range of 0.50 to 1.00. mu.m, and the amount is about 7X 10⁶-1×10⁹Per mm³Preferably about 1X 10⁷-6×10⁸Per mm³E.g. about 1X 10⁷Per mm³、2×10⁷Per mm³. In yet another embodiment, the content of Mn element in solid solution in the core alloy is 0.02-0.10 wt.%, preferably about 0.03-0.08 wt.%, for example about 0.05, 0.06 wt.%.

g) Cold rolled strip

The total rolling reduction of the cold rolling is at least more than 80 percent, and preferably more than 90 percent.

h) Annealing the finished product

The heat treatment of step h) is an annealing treatment. And placing the cold-rolled composite coil in an annealing furnace for final annealing, wherein the annealing temperature is about 200-400 ℃, preferably about 200-300 ℃, for example about 240 ℃. The annealing time is about 1 to 5 hours, for example about 2 hours. After annealing, the aluminum strip with moderate strength and fibrous tissue can be obtained.

The composite aluminium strip of the present invention typically has a thickness of less than about 1.0mm, preferably less than about 0.6mm, for example from about 0.1 to 1.0mm, from about 0.15 to 0.45mm, such as about 0.20 mm.

Through the heat treatment process of the invention, particularly the homogenization treatment of the core alloy in the step b) and the intermediate heat treatment in the step f), the distribution of particles with different equivalent diameters and the content of Mn element in aluminum solid solution in the core alloy are well controlled, so that the composite aluminum strip has high-component P-oriented texture after brazing and excellent post-weld strength.

The treatments of steps g) and h) after step f) do not have much influence on the content of dispersed particle phases and Mn elements in the solid solution of aluminum in the core alloy of the composite aluminum strip. In one embodiment, the size and distribution of the dispersed particle phase in the core alloy of the composite aluminium strip after step f) is the same as the size and distribution of the dispersed particle phase in the core alloy of the composite aluminium strip as supplied. In another embodiment, the content of Mn element in the core alloy of the composite aluminum strip in aluminum solid solution after step f) is the same as the content of Mn element in aluminum solid solution in the core alloy of the composite aluminum strip as supplied.

In one embodiment, the composite aluminum strip of the present invention has a dispersed particle phase number of about 5X 10 in the core alloy in the supplied state, the dispersed particle phase having a dispersed particle phase equivalent diameter in the range of 0.02 to less than 0.50 μm⁹-1×10¹²Per mm³Preferably about 1X 10¹⁰-8×10¹¹Per mm³E.g. about 3X 10¹⁰Per mm³、5×10¹⁰Per mm³. In another embodiment, the dispersed particulate phase has an equivalent diameter in the range of 0.50 to 1.00. mu.m, and the amount is about 7X 10⁶-1×10⁹Per mm³Preferably about 1X 10⁷-6×10⁸Per mm³E.g. about 1X 10⁷Per mm³、2×10⁷Per mm³. In yet another embodiment, the composite aluminum strip of the present invention has a Mn element content in solid solution in aluminum of 0.02 to 0.10 wt.%, preferably about 0.03 to 0.08 wt.%, for example about 0.05, 0.06 wt.%, of the core alloy as supplied.

In one embodiment, the P-oriented texture of the composite aluminum strip of the present invention is about 45% or greater, such as about 48%, 55% or greater, after brazing.

In another embodiment, the composite aluminum strip of the present invention has a post-braze yield strength of about 60 to 75MPa, such as about 65, 72 MPa. In yet another embodiment, the composite aluminum strip of the present invention has a tensile strength after brazing of about 170 and 200MPa, such as about 180, 195 MPa. The mechanical properties are measured using methods conventional in the art, for example GB/T228.1-2010.

The invention also relates to a core alloy. Based on the core material alloy, the core material alloy comprises

(a)0.3 to 1.2% by weight of Si,

1.0 to 2.0 wt.% of Mn,

0.2 to 1.0 wt.% of Cu,

0.1-0.6 wt.% Fe, and

(b) optionally one or more elements selected from:

less than or equal to 0.5 weight percent of Mg,

Less than or equal to 0.3 weight percent of Ti,

Zr of less than or equal to 0.3 weight percent,

the balance being aluminum and inevitable impurity elements.

In the core alloy of the present invention, the number of dispersed particle phases having an equivalent diameter in the range of 0.02 to less than 0.50 μm is about 5X 10⁹-1×10¹²Per mm³Preferably about 1X 10¹⁰-8×10¹¹Per mm³(ii) a And the number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00 mu m is about 7X 10⁶-1×10⁹Per mm³Preferably about 1X 10⁷-6×10⁸Per mm³。

In the core material alloy of the present invention, the content of Mn element in the aluminum solid solution is about 0.02 to 0.10% by weight, preferably about 0.03 to 0.08% by weight.

The core alloy of the present invention is a brazeable core alloy.

As an exemplary aspect, the method for preparing the core material alloy of the present invention includes the steps of:

i) casting an ingot of the core material alloy,

ii) homogenizing heat treatment of the core alloy,

iii) intermediate heat treatment.

Wherein the temperature of the homogenization heat treatment in step ii) is about 450-. The time for the homogenization heat treatment is about 5 to 10 hours, preferably about 5 to 8 hours.

The temperature of the intermediate heat treatment in step iii) is about 200-400 deg.C, preferably about 200-300 deg.C. The time for the intermediate heat treatment is about 1 to 5 hours, preferably about 2 to 3 hours.

The remaining steps are similar to the process for making the composite aluminum strip herein. For example, step ii) may be followed by step iii) and optionally may be preceded by a step of hot rolling or cold rolling. Step iii) may optionally be followed by a step of cold rolling the strip, annealing the finished product.

The P-oriented texture of the core alloy prepared by the above method after brazing is about 45% or more.

The present invention also relates to the use of the composite aluminium strip of the invention or the composite aluminium strip prepared by the method of the invention or the core alloy of the invention for a heat exchanger.

Advantageous effects

The composite aluminum strip is a high-strength composite aluminum strip for brazing with high-component P-oriented texture enhancement. The method solves the problems that in the prior art, due to the fact that the balance between AA3xxx alloy dispersoid phase precipitation and Mn solid solution is difficult to control in large-scale industrial production, Al-Mn series alloy produced by the conventional H24 state production process cannot obtain high-component P oriented texture after brazing, and the alloy is difficult to be strengthened by a texture strengthening method.

Different from the technical method of strengthening the Al-Mn alloy by adding high-content elements such as Si, Mn, Cu and the like through solid solution strengthening and particle strengthening, the aluminum strip further strengthens the post-welding mechanical property of the material by simultaneously utilizing a texture strengthening method. The special process control and the optimization of alloy components are beneficial to controlling the precipitation of Mn-containing dispersed particle phase of the brazing aluminum strip and the solid solubility of Mn element in aluminum solid solution in a proper range before brazing. The aluminum strip has a strong P-oriented texture after brazing, and the P-oriented texture accounts for more than 45 percent of the components, so that the post-welding strength of the aluminum strip is greatly enhanced. Compared with the H24 aluminum strip prepared by the traditional process, the composite aluminum strip produced by the novel process and having the optimized alloy components has the advantage that the mechanical property in the rolling direction is obviously improved, so that the effect of strengthening the alloy property is achieved. The brazing high-strength composite aluminum strip with the high-component P-oriented texture increased can well meet the requirement of light weight of a heat exchanger on material thinning.

The composite aluminum strip has excellent post-welding mechanical property, the post-welding tensile strength of the aluminum strip reaches more than 180MPa without Mg element reinforcement, the yield strength reaches more than 65MPa, and the composite aluminum strip has good corrosion resistance and brazing property.

Examples

The present invention is described in further detail with reference to the following examples, which are not intended to limit the scope of the present invention.

Sample preparation

Sample preparation for example 1

a) Core material alloy, brazing layer alloy and water contact side alloy shown in tables 2, 3 and 4 were respectively subjected to DC casting (direct cooling semi-continuous casting) in the following specific melting process:

adding an industrial pure aluminum ingot into a smelting furnace for melting, wherein the smelting temperature is 730-760 ℃, slagging off, sampling and analyzing, adding alloy elements according to the compositions of the cast ingots of the core layer alloy, the brazing layer alloy and the water contact side alloy in the embodiment 1 in the table 2-4 respectively, standing, stirring, refining, slagging off, adjusting the components, pouring into the standing furnace, stirring again, refining, slagging off, performing online modification treatment, degassing, filtering, and feeding into a casting machine for casting into cast ingots;

b) carrying out homogenization treatment on the core material alloy, wherein the homogenization temperature is 500 ℃, and the time of the homogenization heat treatment is about 8 hours;

c) sawing and milling the homogenized core material, brazing layer alloy and water contact side alloy, and compounding according to the compounding ratio of table 5, wherein the structural schematic diagram is shown in fig. 1 a;

d) hot rolling at 480 deg.C to 3.5 mm;

e) cold rolling to 1.5mm at room temperature;

f) intermediate heat treatment at about 220 ℃ for about 2 hours;

g) cold rolling into a belt: and then rolling to the final thickness of 0.20 mm;

h) annealing of a finished product: and placing the cold-rolled composite coil in an annealing furnace for finished product annealing, wherein the annealing temperature is about 240 ℃, and the annealing time is about 2 hours.

Sample preparation for example 2

The composite aluminium strip of example 2 is a three layer alloy with the core alloy coated on opposite sides with an AA4343 braze layer alloy, the schematic structural diagram of which is shown in figure 1 b. The core alloy composition and braze layer alloy composition are listed in tables 2 and 3. A similar preparation procedure as in example 1 was used, wherein the temperature of the homogenization treatment of the core alloy in step b) was 450 ℃, the time of the homogenization treatment was 8 hours, the temperature of the intermediate heat treatment in step f) was 240 ℃, and the time was 2 hours, and the remaining procedure was the same as that of example 1).

Sample preparation of comparative example 1

The composite aluminium strip of comparative example 1 is a three layer alloy with a core material, a brazing layer and a water contact side, the schematic of the structure being shown in figure 1 a. The core material is prepared by using a conventional H24 state production process, namely, an intermediate heat treatment step of b) homogenizing the core material and f) is not carried out. The core alloy composition, as well as the braze layer alloy and the water-contacting side alloy composition are listed in tables 2-4. The remaining steps were the same as those of example 1.

Sample preparation of comparative example 2

The composite aluminium strip of comparative example 2 is a three layer alloy with the core alloy clad on opposite sides with an AA4343 braze layer alloy, the schematic structural diagram of which is shown in figure 1 b. The core alloy composition and braze layer alloy composition are listed in tables 2 and 3. The core material is prepared by using a conventional H24 state production process, namely, an intermediate heat treatment step of b) homogenizing the core material and f) is not carried out. The remaining steps were the same as those of example 1.

TABLE 2

TABLE 3

TABLE 4

TABLE 5

Performance testing

(1) Particle distribution

And observing the size and distribution of dispersed particle phases in the core alloy in each composite aluminum strip through a scanning electron microscope. The dispersed particle phases in the pictures in a plurality of visual fields (for example, 20) are collected, and the distribution of the dispersed particle phases is calculated. For example, FIG. 2 is a scanning electron microscope photograph of the core alloy of example 1 in the as-supplied state, wherein the white bright spots are in a dispersed particle phase.

The composite aluminum tape of comparative example 1 had a number of dispersed particle phases having an equivalent diameter in the range of 0.02 to less than 0.50 μm of 6X 10 in the core alloy as supplied⁸Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 3X 10⁶Per mm³。

The composite aluminum strip of comparative example 2 had an equivalent diameter in the core alloy as suppliedThe number of dispersed particle phase in the range of 0.02 to less than 0.50 μm is 2X 10⁸Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 4X 10⁶Per mm³。

Example 1 composite aluminium strip in the as-supplied state, the number of dispersed particulate phases in the core alloy having an equivalent diameter in the range 0.02 to less than 0.50 μm was 5 x 10¹⁰Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 2X 10⁷Per mm³。

Example 2 composite aluminium strip when supplied, the core alloy has a number of dispersed particulate phases with an equivalent diameter in the range 0.02 to less than 0.50 μm of 3x 10¹⁰Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 1X 10⁷Per mm³。

The content of Mn element in the core alloy of example 1 in the aluminum solid solution was measured by the resistance method and the thermoelectric method, and the result showed that the content of Mn element in the core alloy in the aluminum solid solution was 0.05 wt% in the state of supplying the composite aluminum strip.

The content of Mn element in the core alloy of example 2 in the aluminum solid solution was measured, and the result showed that the content of Mn element in the core alloy in the aluminum solid solution was 0.06 wt% in the supplied state of the composite aluminum strip.

The content of Mn element in the core alloy of comparative example 1 in the aluminum solid solution was measured, and the result showed that the content of Mn element in the core alloy in the aluminum solid solution was 0.11 wt% in the supplied state of the composite aluminum strip.

The content of Mn element in the core alloy of comparative example 2 in the aluminum solid solution was measured, and the result showed that the content of Mn element in the core alloy in the aluminum solid solution was 0.25 wt% in the supplied state of the composite aluminum strip.

In the preparation of the core alloy of example 1, the number of dispersed particle phases having an equivalent diameter in the range of 0.02 to less than 0.50 μm was 8 × 10 as observed by scanning electron microscopy after homogenizing heat treatment of the core alloy after step b)⁸Per mm³(ii) a Number of dispersed particle phase with equivalent diameter in the range of 0.50 to 1.00 mu mIs 3x 10⁶Per mm³。

In the preparation of the core alloy of example 2, the number of dispersed particle phases having an equivalent diameter in the range of 0.02 to less than 0.50 μm was 5 × 10 as observed by scanning electron microscopy after homogenizing heat treatment of the core alloy after step b)⁸Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 1X 10⁶Per mm³。

Example 1 composite aluminium strip after step f) the number of dispersed particulate phases in the core alloy having an equivalent diameter in the range 0.02 to less than 0.50 μm was 5 x 10¹⁰Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 2X 10⁷Per mm³。

Example 2 composite aluminium strip after step f) the number of dispersed particulate phases in the core alloy having an equivalent diameter in the range 0.02 to less than 0.50 μm was 3x 10¹⁰Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 1X 10⁷Per mm³。

The composite aluminum strip of comparative example 1 had a number of dispersed particle phases in the core alloy after step f) in the range of 0.02 to less than 0.50 μm in equivalent diameter of 6X 10⁸Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 3X 10⁶Per mm³。

The composite aluminum strip of comparative example 2 had a number of dispersed particle phases in the core alloy after step f) having an equivalent diameter in the range of 0.02 to less than 0.50 μm of 2X 10⁸Per mm³(ii) a The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 4X 10⁶Per mm³。

The content of Mn element in the core alloy of example 1 after step f) in the aluminum solid solution was 0.05 wt%.

The content of Mn element in the core alloy of example 2 after step f) in the aluminum solid solution was 0.06 wt%.

The content of Mn element in the core alloy of comparative example 1 in the aluminum solid solution after step f) was 0.11 wt%. Comparative example 2 the content of Mn element in the core alloy in the aluminum solid solution was 0.25 wt%.

The core material alloys of comparative examples 1, 2 were not subjected to a homogenization heat treatment, i.e. step b) was not present. No dispersed particle phase precipitated as observed by scanning electron microscopy after step a).

(2) Simulated brazing

The composite aluminum strips of examples and comparative examples were heated from room temperature to 600 c over about 20 minutes by a brazing furnace, and kept at the temperature for 3 minutes, cooled in the furnace to 500 c, and then opened from the furnace door to take out the sample for air cooling.

(3) Crystal orientation diagram

The composite aluminum strips of examples 1-2 and comparative examples 1-2 were observed for crystal orientation in the composite aluminum strips after brazing using EBSD as shown in fig. 3-6, where gray is the P orientation. It was found that the P orientation accounted for 55% of the composition in the composite aluminum strip of example 1 and 48% of the composition in the composite aluminum strip of example 2. The composite aluminum strip of comparative example 1 had only 23% of the component occupied by the P orientation, and the composite aluminum strip of comparative example 2 had 3% of the component occupied by the P orientation.

(4) Tensile test specimens were prepared according to GB/T228.1-2010 with a gauge length of 50 mm. Then, tensile test was conducted at room temperature at a tensile rate of 20mm/min to test tensile strength, as shown in Table 6.

It can be seen that the tensile strength of the composite aluminum strip of example 1 using the alloy composition and process of the present invention reached 180MPa, and the tensile strength of the composite aluminum strip of example 2 using the Mg-containing alloy composition and process of the present invention reached 195MPa, which is 12MPa and 27MPa higher, respectively, than the tensile strength of the composite aluminum strip of comparative example 1 having a similar core alloy composition but using the conventional H24 temper process. The P-oriented component in the composite aluminum strips of examples 1 and 2 is much higher than that of comparative example 1. The core alloys of examples 1 and 2 and comparative example 1 also differ in particle equivalent diameter distribution and solid solubility of Mn element in the supplied state. The adjustment of the process has important influence on the generation of the strong P texture and the performance improvement of the composite aluminum strip after welding.

When the core alloy not according to the present invention is used in the composite aluminum strip and prepared using the conventional H24 temper process, the particle equivalent diameter distribution and Mn element solid solubility of the core alloy in the obtained product (comparative example 2) are different from those of examples 1 and 2, and the product P orientation texture is much lower than those of examples 1 and 2, and has only lower yield strength and tensile strength.

TABLE 6

	Yield strength R_p0.2(MPa)	Tensile strength R_m(MPa)
			Example 1	65	180
Example 2	72	195
			Comparative example 1	60	168
Comparative example 2	50	150

The present invention is described in detail in the embodiments. It will be apparent to those skilled in the art that modifications and variations can be made in the embodiments without departing from the spirit of the invention. All such modifications and variations are intended to be included herein within the scope of the appended claims.

Claims

1. A composite aluminium strip comprising a core alloy,

wherein the core material alloy comprises based on the core material alloy

(a)0.3 to 1.2% by weight of Si,

1.0 to 2.0 wt.% of Mn,

0.2 to 1.0 wt.% of Cu,

0.1-0.6 wt% Fe,

(b) optionally one or more elements selected from:

less than or equal to 0.5 weight percent of Mg,

Less than or equal to 0.3 weight percent of Ti,

Zr of less than or equal to 0.3 weight percent,

the balance of aluminum and inevitable impurity elements;

wherein the inevitable impurity elements are other elements selected from groups IVB, VB or VIB with a total content of less than or equal to 0.3 wt%, and/or other elements with a single element content of less than or equal to 0.05 wt% and a total content of less than or equal to 0.15 wt%;

wherein the number of dispersed particle phases with the equivalent diameter of 0.02-less than 0.50 μm in the core alloy in the supplied state of the composite aluminum strip is 5 x 10⁹-1×10¹²Per mm³(ii) a And is

The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 7X 10⁶-1×10⁹Per mm³；

Wherein the P-oriented texture of the composite aluminum strip after brazing is more than 45%.

2. The composite aluminum strip of claim 1, wherein the core alloy comprises, based on the core alloy

0.5-1.0 wt.% Si, and/or

1.3-1.8 wt.% of Mn, and/or

0.3-0.8 wt% Cu.

3. The composite aluminum strip of claim 1 or 2, wherein the Mn element of the core alloy is present in the aluminum solid solution in an amount of 0.02 to 0.10 wt.% as supplied.

4. The composite aluminum strip of claim 1 or 2, wherein the composite aluminum strip further comprises a braze layer alloy.

5. The composite aluminum strip of claim 4, wherein the braze layer alloy comprises, based on the braze layer alloy

4-12% by weight of Si,

Fe of less than or equal to 0.6 weight percent,

Mn of not more than 1.0 wt%,

Cu of not more than 1.0 wt%,

Less than or equal to 1.0 weight percent of Zn,

the balance of aluminum and inevitable impurity elements;

6. The composite aluminum strip of claim 1 or 2, optionally comprising a water-contact side alloy, wherein

Based on the water-contact side alloy, the water-contact side alloy comprises

0.5 to 5.5 wt.% of Zn,

0 to 1.5% by weight of Si,

0 to 2.0 wt.% of Mn,

Fe of less than or equal to 0.6 weight percent,

0-1.0 wt.% of Mg,

the balance of aluminum and inevitable impurity elements;

7. The composite aluminum strip of claim 4, wherein the brazing layer alloy is clad on one or both sides of the core alloy.

8. The composite aluminum strip of claim 1 or 2, wherein the total thickness of the composite aluminum strip is 0.10 to 1.00 mm.

9. A method of making the composite aluminum strip of any one of claims 1 to 8, comprising

b) homogenizing and heat-treating the core material alloy,

e) cold rolling the mixture to obtain the finished product,

f) performing intermediate heat treatment on the mixture,

g) cold-rolling the mixture into a belt,

h) annealing the finished product;

wherein the temperature of the homogenization heat treatment in the step b) is 450-550 ℃, and the time of the homogenization heat treatment is 5-10 hours;

the temperature of the intermediate heat treatment in the step f) is 200-400 ℃, and the time of the intermediate heat treatment is 1-5 hours.

10. The method of making a composite aluminum strip of claim 9, wherein

The number of dispersed particle phases in the core alloy after step b) having an equivalent diameter in the range of 0.02 to less than 0.50 μm is 1X 10⁸-1×10¹⁰Per mm³(ii) a And is

The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 2X 10⁵-1×10⁷Per mm³。

11. A method of making a composite aluminium strip according to claim 9 or 10, wherein

The equivalent diameter in the core alloy of the composite aluminium strip after step f) is in the range of 0.02 to less than 0.50 μmThe number of dispersed particle phase of (2) is 5X 10⁹-1×10¹²Per mm³(ii) a And is

The number of dispersed particle phases having an equivalent diameter in the range of 0.50 to 1.00. mu.m is 7X 10⁶-1×10⁹Per mm³。

12. A method of making a composite aluminium strip according to claim 9 or 10, wherein

The content of Mn element in the composite aluminum strip core alloy after step f) in the aluminum solid solution is 0.02-0.10 wt%.

13. A core alloy, wherein the core alloy comprises, based on the core alloy

(a)0.3 to 1.2% by weight of Si,

1.0 to 2.0 wt.% of Mn,

0.2 to 1.0 wt.% of Cu,

0.1-0.6 wt% Fe,

(b) optionally one or more elements selected from:

less than or equal to 0.5 weight percent of Mg,

Less than or equal to 0.3 weight percent of Ti,

Zr of less than or equal to 0.3 weight percent,

the balance of aluminum and inevitable impurity elements;

wherein the number of dispersed particle phases having an equivalent diameter in the range of 0.02 to less than 0.50 μm in the core alloy is 5 x 10⁹-1×10¹²Per mm³(ii) a And is

Wherein the P orientation texture of the core alloy after brazing is more than 45%.

14. The core alloy of claim 13, wherein the Mn element content in the core alloy in solid solution with aluminum is 0.02 to 0.10 wt.%.

15. Use of the composite aluminium strip according to any one of claims 1 to 8 or the composite aluminium strip produced by the method according to any one of claims 9 to 12 or the core alloy according to any one of claims 13 to 14 in a heat exchanger.