ES2779052T3 - Starting material for high strength aluminum alloy fin for heat exchanger - Google Patents

Abstract

A starting material for aluminum alloy fin comprising 0.9-1.3% by weight of Si, 0.45-0.75% by weight of Fe, 0.10-0.3% by weight of Cu , 1.3-1.7% by weight of Mn and 1.30-2.2% by weight of Zn, with the balance being Al, where optionally Cr and / or Zr are present in the starting material for fin of aluminum alloy in an amount of up to 0.03% by weight each, and wherein optionally in addition the starting material for aluminum alloy fin contains other minor elements in an amount of less than 0.05% by weight.

Description

DESCRIPTION

Starting material for high strength aluminum alloy fin for heat exchanger

Field of the invention

The present invention relates to the fields of materials science, materials chemistry, metallurgy, aluminum alloys, aluminum fabrication, and related fields. The present invention provides new aluminum alloys for use in the production of heat exchanger fins, which are in turn used in various heat exchange devices, for example, motor vehicle radiators, condensers, evaporators and devices. related.

Background

There is a need for a high strength aluminum fin starting material for use in various heat exchanger applications, including automotive radiators. There is also a need to obtain a starting material for aluminum alloy fin with excellent mechanical properties prior to welding, good behavior during welding, that is, greater resistance to buckling of the welded material and reduced erosion of the fins, as well as good post-weld conductivity and resistance characteristics for use in high performance heat exchanger applications.

JP 2002-161324 A is directed to an aluminum alloy fin material for a heat exchanger, wherein the aluminum alloy fin material comprises 1.0% to 2.0% Mn, 0 , 5 to 1.3% Si, 0.1 to 0.8% Fe, 0.21 to 0.5% Cu, 1.1 to 5% Zn, a Mn component ratio : Si (% Mn /% Si) is 1.0 to 3.5, a component ratio of Zn: Cu (% Zn /% Cu) that is 5 to 15, plus one or two kinds of 0.05 at 0.3% Zr or from 0.05 to 0.3% Cr, the remainder being Al with unavoidable impurities and a tensile strength of 160 to 270 MPa.

JP H10-88265 A is directed to an aluminum alloy fin material for heat exchangers, wherein the aluminum alloy has a composition consisting of, by weight,> 1.5 to 2.2% Mn , from 0.5 to 1.2% of Si, from 0.1 to 0.6% of Fe,> 2 to 5% of Zn, from 0.1 to 0.6% of Cu, and the rest Al with unavoidable impurities and containing, if necessary, one or both of <0.05% In and <0.05% Sn and further containing, if necessary, one or more types of <0.2% of Mg, <0.25% Zr and <0.25% Cr.

Summary

The invention is defined in the appended claims.

The present invention provides an aluminum alloy fin starting material for use in heat exchanger applications, such as automotive heat exchangers. This aluminum alloy fin alloy starting material was manufactured by direct chill (ED) casting. The aluminum alloy fin starting material according to embodiments of the present invention has one or more of the following properties: high strength, desirable post-weld mechanical properties, desirable sag resistance, desirable corrosion resistance, and desirable conductivity. The aluminum alloy fin starting material according to some embodiments of the present invention shows larger grain dispersoids and improved strength before welding. Some embodiments of the starting material for aluminum alloy fins are produced in a desirable pre-weld temper, eg, H14.

The improved aluminum alloy fin starting material can be used in various applications, for example heat exchangers. In one embodiment, the aluminum alloy fin starting material can be used in automobile heat exchangers, such as radiators, condensers, and evaporators. In some embodiments, the aluminum alloy fin starting material is useful for high performance, light weight automobile heat exchangers. In some other embodiments, the aluminum alloy fin stock can be used for other welded applications, including, but not limited to, HVAC HVAC applications. Other objects and advantages of the invention will be apparent from the following detailed description of embodiments of the invention.

Description

The present invention provides an aluminum alloy fin starting material as defined in claim 1. This aluminum alloy fin alloy starting material was manufactured by direct cooling casting (ED). Some embodiments of the aluminum alloy fin starting material have one or more of improved strength, improved corrosion resistance, or improved buckling resistance. In some embodiments, the aluminum alloy fin stock exhibits desirable pre-weld tempering (H14) mechanical properties and desirable post-weld mechanical properties, buckling resistance, corrosion resistance, and conductivity. In some other embodiments, the aluminum alloy fin stock exhibits a larger post-weld grain size and improved pre-weld strength. The starting material for fin Aluminum alloy can be used in various applications, for example, heat exchangers. In one example, the aluminum alloy fin starting material can be used in automobile heat exchangers, such as radiators, condensers, and evaporators.

Compositions of a starting material for aluminum alloy fins are within the scope of the present invention. Some exemplary embodiments of the aluminum alloy fin starting material compositions are described below. All% values used hereinafter and throughout this document in reference to constituent amounts of aluminum alloy fin starting material compositions are% by weight (wt%).

The starting material for aluminum alloy fin according to the present invention comprises 0.9-1.3% Si, 0.45-0.75% Fe, 0.10-0.30% Cu, 1.3-1.7% Mn and 1.30-2.2% Zn, remainder aluminum, where optionally Cr and / or Zr are present in the starting material for aluminum alloy fin in an amount of up to 0.03% by weight each, and wherein optionally furthermore the starting material for aluminum alloy fin contains other minor elements in an amount less than 0.05% by weight.

In one embodiment, the starting material for aluminum alloy fin comprises 0.9-1.2% Si, 0.50-0.75% Fe, 0.15-0.30% Cu, 1, 4-1.6% Mn and 1.4-2.1% Zn, rest aluminum.

In another embodiment, the starting material for ED fin comprises 0.9-1.1% Si, 0.10-0.25% Cu, 0.45-0.7% Fe, 1.4-1 , 6% Mn, and 1.4-1.7% Zn, the rest being Al.

In yet another embodiment, the aluminum alloy fin starting material comprises 0.90-1.0% Si, 0.15-0.25% Cu, 0.5-0.6% Fe, 1, 5-1.6% Mn, and 1.5-1.6% Zn, rest Al.

In yet another embodiment, the starting material for aluminum alloy fin comprises 0.9-1% Si, 0.2% Cu, 0.5-0.6% Fe, 1.5-1, 6% Mn, and 1.5-1.6% Zn, rest Al.

In yet another embodiment, the aluminum alloy fin starting material comprises 0.9-0.95% Si, 0.2% Cu, 0.5-0.6% Fe, 1.5- 1.6% Mn, and 1.5-1.6% Zn, rest Al.

In another embodiment, the aluminum alloy fin starting material comprises 0.90-0.95% Si, 0.15 0.20% Cu, 0.55% Fe, 1.5% Mn and 1.5% Zn, rest Al.

In yet another embodiment, the aluminum alloy fin starting material comprises 0.95% Si, 0.15% Cu, 0.55% Fe, 1.5% Mn, and 1.5% Zn. , rest Al.

In yet another embodiment, the starting material for aluminum alloy fin comprises 0.90-0.95% Si, 0.15-0.20% Cu, 0.5-0.6% Fe, 1 , 5% Mn and 1.5% Zn, rest Al.

In yet another embodiment, the aluminum alloy fin starting material comprises 1.0-1.2% Si, 0.2 0.3% Cu, 0.5-0.6% Fe, 1, 4-1.55% Mn, and 1.9-2.1% Zn, rest Al.

In yet another embodiment, the aluminum alloy fin starting material comprises 0.95 ± 0.05% Si, 0.2% ± 0.05 Cu, 0.6% ± 0.1 Fe, 1 , 45% ± 0.05 of Mn, and 1.55% ± 0.1 of Zn, rest Al.

In a further embodiment, the starting material for the aluminum alloy fin comprises 1.15% ± 0.05 of Si, 0.25% ± 0.05 of Cu, 0.6% ± 0.1 of Fe, 1 , 5% ± 0.05 of Mn, and 2.0% ± 0.1 of Zn, rest Al.

Optionally, Cr and / or Zr or other grain size control elements may be present in the aluminum alloy fin starting material compositions in an amount of up to 0.03% each. It should be understood that the aluminum alloy fin starting material compositions described herein may contain other minor elements, sometimes referred to as unintentional elements, in an amount typically less than 0.05%.

Some embodiments of the aluminum alloy fin starting materials of the present invention show a higher solidus temperature, referred to as melt onset, which leads to better core shrinkage, a phenomenon in which alloy units of Welded aluminum does not have the desired shape. While not wishing to be bound by the following statement, it is believed, based on differential scanning calorimetry (DSC) measurements and Thermo-Calc® software (Stockholm, Sweden) simulations, that reducing the Si content and the Si content Zn and increasing Mn content in aluminum alloy fin starting material compositions can lead to a higher melt initiation temperature (solidus), which contributes to reduced core shrinkage. In one example, an aluminum alloy fin starting material composition according to embodiments of the present invention exhibits a solidus temperature greater than 617 ° C and a post weld coarse grain size of about 400 pm. In a further example, limit the Si content of the alloy to 0.9-1% (preferably 0.9-0.95%) and the Zn content to 1.5-1.6%, while keeping the Mn content relatively high (for example, about 1.5%) increases the solidus temperature of the alloy, which, in turn, strengthens the material to the solder temperature, so that it can resist buckling or high temperature creep that can cause core shrinkage.

Some embodiments of the present invention relate to starting materials for aluminum alloy fins that have a defined composition and are obtained by processes that include defined process steps and conditions. A combination of defined composition and production process can lead to improved properties of the aluminum fin starting materials. An example of such improved properties is improved pre-weld mechanical properties. Improved pre-weld mechanical properties (also referred to as "in pre-weld condition" properties) result in improved resistance to fin crushing during assembly, while maintaining adequate buckling resistance and thermal conductivity afterward. welding (post-welding).

The processes of producing starting materials for aluminum alloy fins in accordance with embodiments of the present invention involve the step of producing an ingot by a direct chill (DE) casting process, which is commonly used throughout the industry. of aluminum, whereby a large ingot of ~ 1.5 mx 0.6 mx 4 m is cast from a large holding furnace supplying metal to a shallow mold or molds supplied with cooling water. The solidifying ingot is continuously cooled by the direct impact of the cooling water and is slowly withdrawn from the base of the mold until the complete ingot or ingots are completed. After cooling after the casting process, the ingot rolling surfaces are machined to eliminate segregation and surface irregularities. The machined ingot is preheated for hot rolling. Preheat temperature and duration are controlled at low levels to preserve large grain size and high post-weld strength of the finished fin stock. Several ingots (approximately 8 to 30) are loaded into a furnace and preheated with gas or electricity to rolling temperature. The period of maintaining a temperature reached by preheating can also be called "soaking" or "soaking". In one embodiment, the minimum soak time at about 480 ° C is about 2 hours (in other words, at least 2 hours). In another embodiment, the soak time is 4-16 hours at 480 ° C. Aluminum alloys are typically rolled in the range of about 450 ° C to about 560 ° C. If the temperature is too cold, the rolling loads are too high, and if the temperature is too high, the metal can be too soft and break in the rolling mill.

The processes for the manufacture of aluminum alloy fin starting materials involve one or more cold rolling steps. Each of the cold rolling stages, in turn, may involve multiple cold rolling passes. A cold rolling stage is characterized by a "% cold working" or% TF achieved. Generally,% TF can be defined as the degree of cold rolling applied to the starting material for aluminum alloy fin. As used herein,% TF is calculated as:

0y Y p - caH ^ re in ic ia l-c a lib re end a l ^ ^ Q Q 0y

initial gauge

Achieving a specified range or value of% TF may be desirable to achieve the required strength range of the aluminum fin starting material. Some embodiments of the starting materials for aluminum alloy fins are produced by processes that involve a cold rolling step that achieves a TF of 25-35%. In some examples, a cold rolling step that achieves a% TF of 25% or 29% may be employed. In some cases, increasing the% TF, for example up to 35%, leads to an increase in the pre-weld tensile strength of the aluminum alloy fin starting material, which in turn reduces beneficially flattening the fin during radiator mounting. In some other cases, increasing the% TF, however, may be undesirable, as it can lead to a finer post-weld grain size due to an increase in driving force for recrystallization, resulting in reduced strength. to buckling.

The processes for making aluminum alloy fin starting materials involve an inter annealing step to achieve the desired properties of the aluminum alloy fin starting material in accordance with embodiments of the present invention. The term "inter-anneal" or "inter-anneal" (IR) refers to a heat treatment applied between cold rolling stages. IR temperature can affect the properties of starting materials for aluminum alloy fins according to embodiments of the present invention. For example, an investigation of the IR temperature used in processes to make certain embodiments of the starting materials for aluminum alloy fins showed that reducing the IR temperature from 400 ° C to 350 ° C resulted in a size of coarser grain after welding. In some embodiments of the aluminum alloy fin starting materials, a combination of% TF and IR temperature employed in the production process results in desirable properties. In one example, a combination of IR temperature of 350 ° C and 35%% TF led to a beneficial combination of post weld grain size and buckling resistance of the aluminum fin starting material. In another example, a combination of IR temperature of 300 ° C and% TF of the 25 % led to a beneficial combination of post weld grain size and sag resistance of the aluminum fin starting material. In another example, a combination of IR temperature and% TF during aluminum alloy fin starting material processing during H14 tempering resulted in improved fin crush resistance. Therefore, aluminum alloy fin starting material production processes employing specified IR temperature and% TF, leading, in some examples, to higher pre-weld tensile strength and better strength flattening of the fins during assembly is included within the embodiments of the present invention.

Once preheated, the ingot is hot rolled to form a coil which is then cold rolled. The cold rolling process takes place in several stages, and an inter-annealing stage is employed between the cold rolling stages to recrystallize the material before the final cold rolling stage. An IR temperature in the range of 275-400 ° C is employed. An AI temperature in the range of about 300-400 ° C, 300-450 ° C, 340-460 ° C, or 325-375 ° C can be employed. For example, an IA temperature of about 300 ° C, 350 ° C, or 400 ° C can be employed in aluminum alloy fin material production processes in accordance with embodiments of the present invention. After inter annealing, the aluminum alloy fin starting material is cold rolled in the final cold rolling stage to obtain the desired final gauge or thickness. After the final cold rolling stage, the aluminum alloy fin starting material can be cut into narrow strips suitable for making radiators and other automobile heat exchangers. In the production processes of aluminum alloy fin starting materials, the% TF used in the final cold rolling stage is 20-35% or 25-35%, for example approximately 25% or 29 %.

Various combinations of production parameters may be beneficially employed in the processes for aluminum alloy fin material production processes in accordance with embodiments of the present invention. In one example,% TF in the range of 25-35% is employed in the final rolling stage, resulting in improved pre-weld creep strength and tensile strength of the fin starting materials. made of aluminum alloy, which, in turn, leads to a reduction in the occurrence of fin crushing during assembly. In another example, selecting an IR temperature of about 350 ° C results in a larger post weld grain size. In a further example, the use of a% TF of about 29% during the final cold rolling stage further increases the post weld grain size. In yet another example, inter-anneal at 350 ° C for 4 hours in combination with 29% TF is used in the final cold rolling stage, resulting in a material with desirable characteristics of good pre-heat resistance. welding and large post-weld grain size, high thermal conductivity and good buckling behavior. In yet another example, interanneal at 400 ° C is employed for an average of about 3 hours, followed by the application of a% cold work (TF) of about 29% to achieve the final gauge. In yet another example, soaking at about 480 ° C is employed for an average of 4 hours during the hot rolling stage, in combination with inter-annealing at about 300-400 ° C and% TF in the final rolling stage. cold of approximately 25-35% to the final size. In yet another example, soak at 480 ° C for 4-16 hours is employed in the hot rolling stage in combination with inter-anneal at 350 ° C and 29% TF% in the final rolling stage. In yet another example, soak at 480 ° C for 4-16 hours is employed in the hot rolling stage in combination with inter-anneal at 400 ° C and a% TF of 29% in the final rolling stage. In a further example, soak at 480 ° C for an average of 4 hours is employed in the hot rolling stage in combination with inter-anneal at 350 ° C and 35%% Tf in the final rolling stage. In a further example, inter-anneal at 325-375 ° C and 20-35% TF is employed, such as inter-anneal at 300 ° C and 25% TF in the final stage of cold rolling.

The starting materials for aluminum alloy fins produced in accordance with some embodiments of the present invention are produced as sheets whose gauge (thickness) varies between 45 µm and 80 µm. The starting material for aluminum alloy fin according to the embodiments of the present invention has one or more of the following properties: minimum ultimate tensile strength (UTS) of 130 MPa (in other words, 130 MPa or more, or at least 130 MPa) measured after welding (eg, 134 or 137 MPa); average conductivity value of about 43%, about 41.5%, about 42.7% or about 43.3% (International Annealed Copper Standard (IACS)); a standard calomel electrode (SCE) open circuit potential corrosion value of -680mV or less, -700mV or less, or -740 or less (e.g. -710mv, -720mv, -724mv, -725 mv, -743 mv, -740mV or -758 mV); a buckling value between 7 mm, where the final gauge was 47.5 pm and 5 mm, where the final gauge was 50 pm, with a cantilever length of 35 mm. The above properties of aluminum alloy fin starting material sheets are measured after applying a faster welding cycle, whereby the material is heated to a temperature of 605 ° C and cooled to room temperature in a period of approximately 20 minutes, to simulate the time and temperature profile of a commercial welding process. The starting material for aluminum alloy fin according to embodiments of the present invention may have a UTS pre-weld in the range of 180-220 MPa (eg 185 or 190 MPa). The starting material for aluminum alloy fin according to embodiments of the present invention may also have a grain size> 200 µm, eg 200 or 400 µm.

The following examples will serve to further illustrate the present invention, however, without at the same time constituting any limitation thereto.

Example 1

An aluminum alloy fin stock was manufactured by a process involving ED casting, preheating the ingot at 480 ° C for about 8 hours, followed by hot rolling to about 2.5mm, cold rolling, and inter-annealed at 350 ° C for approximately 2 hours before the final cold rolling stage. The starting material composition range for aluminum alloy fin was within the following specification: 1.1 ± 0.1% Si, 0.6 ± 0.1% Fe, 0.2 ± 0.05 % Cu, 1.4 ± 0.1% Mn and 1.50 ± 0.1% Zn, with the remainder Al. The starting material for aluminum alloy fin produced had a gauge that varied between 49 and 83 pm. The starting material for aluminum alloy fin had a minimum maximum tensile strength of ~ 130MPa. The aluminum alloy fin starting material had an average post-weld conductivity of ~ 43 IACS and an open-circuit potential corrosion value against SCE of -741 mV. These values were measured after applying a simulated welding cycle, whereby the sample was heated to a temperature of 605 ° C and cooled to room temperature over a period of approximately 20 minutes to simulate the time and temperature profile of a commercial welding process.

Example 2

Two aluminum alloy fin starting material samples were fabricated by a process involving ED casting, followed by hot rolling with preheating at 480 ° C for 4-16 hours, cold rolling, and inter-annealing at 350 ° C for the first sample and 400 ° C for the second sample, before the final cold rolling a% TF of 29%. The composition of the first sample was: 0.95% Si, 0.6% Fe, 0.2% Cu, 1.45% Mn and 1.55% Zn, with the remainder Al. The composition of the second sample was: 1.15% Si, 0.6% Fe, 0.25% Cu, 1.5% Mn and 2% Zn, with the remainder Al. The starting material for Aluminum alloy fin had a post-weld ultimate tensile strength of ~ 134 MPa for the first sample and ~ 137 MPa for the second sample. The aluminum alloy fin stock had an average post-weld conductivity of ~ 42.7 IACS for the first sample and ~ 43.3 IACS for the second sample. The aluminum alloy fin starting material had an open circuit potential corrosion value against SCE of -710mV for the first sample and -743mV for the second sample. The aluminum alloy fin starting material had a grain size of 400 µm for the first sample and 200 µm for the second sample. The starting material for aluminum alloy fin exhibited pre-weld UTS of 185 MPa for the first sample and 190 MPa for the second sample. Comparison between the two samples revealed that both samples produced attractive mechanical properties, although the potential open-circuit corrosion value of the first sample was lower, indicating that an increase in Zn content may be desirable. The second sample had an advantageously lower open circuit potential corrosion value.

Claims (10)

1. A starting material for aluminum alloy fin comprising 0.9-1.3 % by weight of Si, 0.45-0.75 % by weight of Fe, 0.10-0.3% by weight of Cu, 1.3-1.7% by weight of Mn and 1.30-2.2% by weight of Zn, with the remainder as Al, where optionally Cr and / or Zr are present in the starting material for aluminum alloy fin in an amount of up to 0.03% by weight each, and wherein optionally in addition the starting material for aluminum alloy fin contains other minor elements in an amount less than 0.05% by weight . 2. The aluminum alloy fin starting material of claim 1, comprising 0.9-1.2% by weight of Si, 0.5-0.75% by weight of Fe, 0.15-0 , 3% by weight Cu, 1.4-1.6% by weight Mn and 1.4-2.1% by weight Zn, with the remainder being Al or comprising 0.9-1.1% by weight of Si, 0.5-0.6% by weight of Fe, 0.15-0.25% by weight of Cu, 1.5-1.6% by wt Mn and 1.5-1.6 wt% Zn, with the remainder as Al. 3. The aluminum alloy fin starting material of claim 1, comprising 0.90-1.0% by weight of Si, 0.55% by weight of Fe, 0.15-0.20% in weight of Cu, 1.5% by weight of Mn and 1.5% by weight of Zn, and with the remainder as Al, in particular comprising 0.95% by weight of Si and 0.15% by weight of Cu. 4. The aluminum alloy fin starting material of claim 1, comprising 1.0-1.2% by weight of Si, 0.5-0.6% by weight of Fe, 0.2-0 , 3% by weight of Cu, 1.4-1.55% by weight of Mn and 1.9-2.1% by weight of Zn, with the remainder being Al or comprising 0.95% Si, 0.2% Cu, 0.6% Fe, 1.45% Mn and 1.55% Zn, rest Al or comprising 1.15% by weight of Si, 0.25% by weight of Cu, 0.6% by weight of Fe, 1.5% by weight of Mn and 2.0% by weight of Zn, remainder Al. 5. A heat exchanger comprising the aluminum alloy fin starting material of any one of claims 1 to 4. 6. The heat exchanger of claim 5, wherein the heat exchanger is an automobile heat exchanger or wherein the heat exchanger is a radiator, a condenser, or an evaporator. 7. Use of the aluminum alloy fin starting material of any one of claims 1 to 4 for the manufacture of heat exchanger fins. A process for manufacturing the aluminum alloy fin starting material of any of claims 1 to 4, comprising direct cooling casting of an aluminum alloy into an ingot; preheating the ingot at 450-500 ° C for 2 to 16 hours; hot rolling of the preheated ingot; cold rolled ingot; interannealed at a temperature of 275 to 400 ° C; and, After inter-annealing, perform a final cold rolling stage to achieve a% cold work,% TF, of 20-35%. The process of claim 8, wherein the ingot is preheated at 480 ° C for 2-16 hours or wherein the ingot is preheated for 2-12 hours. The process of claim 8, wherein the inter-anneal temperature is 325 to 375 ° C or where the inter-anneal temperature is 300, 350 or 400 ° C or where the inter-anneal temperature is 300 ° C and the% TF is 25% or where the inter-anneal temperature is 350 ° C or 400 ° C and the% TF is 29%.