CN115971720A - Self-brazing aluminum-based brazing filler metal and preparation method thereof - Google Patents
Self-brazing aluminum-based brazing filler metal and preparation method thereof Download PDFInfo
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Abstract
The invention discloses a self-brazing aluminum-based brazing filler metal and a preparation method thereof, the self-brazing aluminum-based brazing filler metal comprises 4-8% of brazing flux, 4-20% of total Si, and the balance Al, wherein the oxygen content is less than 450ppm, the relative density is more than 95%, the Si grain size is about 10 mu m, and the preparation method comprises the following steps: 1) Preparing a first brazing filler metal, wherein the brazing filler metal is brazing flux-coated Al-Si alloy composite powder, and the composite powder comprises 4.5-8.5% of brazing flux and the balance of Al-Si alloy (0-5 Si); 2) Preparing a second brazing filler metal, wherein the brazing filler metal is Al-Si alloy (30-60 Si) powder; 3) Mixing powder according to component requirements in the range of the ratio of the first aluminum brazing filler metal to the second aluminum brazing filler metal being 75-97.5; 4) Carrying out hot isostatic pressing on the mixed powder by vacuumizing the envelope; 5) Peeling and machining to obtain the self-brazing aluminum solder, wherein the obtained self-brazing aluminum solder has good brazing activity and good ductility, is suitable for batch production and small-batch customization, and simplifies the existing brazing process.
Description
Technical Field
The invention relates to the field of self-brazing of aluminum alloy, in particular to a self-brazing aluminum-based brazing filler metal and a preparation method thereof.
Background
Aluminum or aluminum alloy is used more and more widely due to its light weight, excellent mechanical properties and good thermal properties, and has gained more and more attention as a key technique for connecting aluminum or aluminum alloy parts, namely brazing.
The aluminum brazing refers to brazing with the brazing temperature higher than 450 ℃, two aluminum alloy parts are used as base materials, al-Si series aluminum-based brazing filler metal (or filling material) is placed between connecting surfaces, the aluminum-based brazing filler metal is melted through heating, the base materials are not melted, and the connection between the parts is obtained after cooling. However, aluminum is an extremely active element, and when it comes into contact with oxygen, an aluminum oxide film is rapidly formed on the aluminum surface, which inhibits the progress of brazing and impairs the bonding strength. Thus, in many brazing techniques, the brazing process involves having to place flux (in addition to vacuum brazing) on the joint surface of the parts, the flux having a melting point lower than that of the braze, the flux first breaking the surface oxide film during brazing, after which the braze melts, promoting wetting, flow and filling of the braze with the parent metal, resulting in a robust brazed joint.
The aluminum flux is a non-metallic component and is hard to be combined with the Al — Si based alloy of metallic properties, and therefore, the flux of the early technology is used separately from the brazing filler metal, for example, an aluminum-based brazing filler paste method (flux + brazing filler metal powder + binder + solvent) is generally used, or a method of coating the brazing filler metal on the brazing portion of the aluminum part and then placing the aluminum-based brazing filler metal on the brazing portion is used, but although these methods are still in use, the method generally has problems of complicated brazing process, many steps, high cost, long time, and the like.
Therefore, it is desirable to eliminate the flux coating step to simplify the brazing process, improve the brazing quality, and reduce the cost by combining the flux with the aluminum filler metal to form the composite aluminum-based filler metal.
For example, U.S. patent No. 8978, entitled "seamless, annular brazing material and method for making same", discloses a self-fluxing aluminum brazing material which is formed by a powdered brazing filler metal and a brazing flux in a predetermined ratio to form a homogeneous mixture; then pressing at room temperature; hot extrusion to form a tube having a relative density greater than 90%; then cutting; forming a seamless annular self-brazing flux ring for aluminum pipe brazing connection. However, the inevitable oxide film (oxygen content) on the surface of the brazing filler metal raw material leads to a higher dosage of the brazing flux, and the brazing filler metal is brittle and is not favorable for further deep processing.
In the US patent specification 8696829 "brazed product comprising flux and filler metal mix" and method for making same, a self-fluxing aluminium brazing material is disclosed, by filling 0.5-5mm coarse particles with metal (brazing filler metal), rolling the filled particles in a rotating drum at a temperature of 120-150 ℃, dropping a low viscosity mixture of flux and water into the rolling particles at a particle temperature above 100 ℃, attaching a layer of flux powder to the surface of the filled particles, and subsequently extruding a self-fluxing brazing filler wire at a pressure below 5000bars and below 300 ℃ below the flux melting point, however, this process also suffers from the problem of oxide film on the surface of the filled metal and is limited to wire, e.g. 1-3mm brazing wire, due to the high initial investment and limited application range using high pressure equipment.
US8871356 discloses a self-fluxing brazing member, an assembly comprising said brazing member and a method for producing a brazing member, which self-fluxing brazing member is produced by using Osprey spray deposition process, has an oxygen content of less than 350ppm, good flux dispersion, adequate rolling ability and excellent brazing performance, is used only for a brazing layer of an aluminum composite sheet, and has disadvantages of low raw material utilization, high initial investment, high cost, difficulty in obtaining large size ingots (typically ingot sizes less than 600 mm), limited composition, unsuitability for high flux content and high Si content aluminum alloy compositions, or reduction in self-fluxing brazing member ductility and subsequent processing difficulties.
Therefore, in order to overcome the disadvantages or shortcomings, it is desirable to provide a self-fluxing aluminum-based solder with good soldering performance, low oxygen content, and good plasticity/ductility, and to economically manufacture various self-fluxing aluminum-based solders of plate, sheet, wire, foil, ring, or different shapes.
Disclosure of Invention
The invention aims to solve the defects in the prior art and provides a self-brazing aluminum-based brazing filler metal and a preparation method thereof.
In order to achieve the purpose, the invention adopts the following technical scheme:
according to one aspect of the present invention, a method for preparing a self-brazing aluminum-based brazing filler metal is provided.
A preparation method of self-brazing aluminum-based brazing filler metal comprises the following steps:
step 1: preparing a first aluminum brazing filler metal, wherein the brazing filler metal is brazing flux-clad Al-Si alloy composite powder, and the composite powder specifically comprises the following components in percentage by weight:
4.5-8.5% of flux, 0-5% of Si and the balance of Al, wherein the grain size of Si is 10 mu m;
step 2: preparing a second aluminum brazing filler metal, wherein the brazing filler metal is Al-Si alloy powder, and the alloy powder specifically comprises the following components in percentage by weight:
30-60% of Si and the balance of AL, the Si grain size being 10 μm;
and step 3: and (3) in the ratio of the first aluminum brazing filler metal to the second aluminum brazing filler metal of 75-97.5:2.5-25, mixing the powder according to the requirements of the raw material components;
and 4, step 4: carrying out hot isostatic pressing on the mixed powder by vacuumizing the envelope;
and 5: peeling and machining to obtain the finished product, thus obtaining the self-fluxing aluminum solder.
Further, the flux is a fluorine-based flux, a chlorine-based flux, or a combination of a fluorine-based flux and a chlorine-based flux, wherein:
a fluorine-based flux comprising: k 3 AlF 4 、K 2 AlF 5 、K 2 AlF 5 ·H 2 O、K 3 AlF 6 、AlF 3 、KZnF 3 、K 2 SiF 6 、Cs 3 AlF 6 、CsAlF 4 ·2H 2 O or Cs 2 AlF 5 .H 2 O；
A chlorine-based flux comprising: naCl, KCl, liCl or ZnCl 2 。
Further, in the step 1, the flow of the step of preparing the first aluminum brazing filler metal is as follows:
melting Al-Si alloy in a melting furnace at 780 ℃;
transferring to a tundish, and enabling the molten alloy to flow out of a hole at the bottom of the tundish to form a molten alloy flow beam to enter an atomization chamber protected by N2 atmosphere;
injecting nitrogen to convert the melt alloy flow beam into aluminum alloy atomized liquid drops;
the atomized liquid drops enter a brazing flux powder fluidized bed with the granularity of 20 mu m, and the brazing flux is coated with the brazing flux under the inert atmosphere;
and cooling to obtain the first aluminum brazing filler metal composite powder.
Wherein the first aluminum brazing filler metal has a particle size of 300 μm or less and an oxygen content of 300ppm or less.
Further, in step 2, the step flow of preparing the second aluminum brazing filler metal is as follows:
melting Al-40Si alloy in a melting furnace at a temperature of 850 ℃;
transferring the alloy to a tundish, and enabling the alloy to flow out from a hole at the bottom of the tundish to form a melt alloy flow beam to enter an atomization chamber protected by N2 atmosphere;
injecting nitrogen to convert the melt alloy flow beam into atomized liquid drops of the aluminum alloy;
and cooling to obtain second aluminum brazing filler metal alloy powder.
Wherein the particle size of the second aluminum brazing filler metal is 400 [ mu ] m or less, and the oxygen content is 400ppm or less.
Further, in step 3, the flow of the powder mixing step is as follows: and (2) putting the first aluminum brazing filler metal and the second aluminum brazing filler metal into a double-cone mixer according to the proportion of 80.
Further, in step 4, the procedure of evacuating the envelope and hot isostatic pressing comprises: putting the prepared mixed powder into an aluminum sheath, and vacuumizing the sheath at 350 ℃ under the condition that the vacuum degree is lower than 1 x 10 < -3 > Pa;
hot isostatic pressing is carried out at the temperature of 450 ℃ and the pressure of 180MPa for 4 hours to obtain a self-fluxing aluminum-based brazing filler metal blank.
Further, in step 5, the self-brazing aluminum-based brazing filler metal is made into a plate, a sheet, a wire, a foil, a ring or a special-shaped self-brazing aluminum-based brazing filler metal.
According to another aspect of the present invention, there is provided a self-brazing aluminum-based brazing filler metal prepared by the above method.
A self-fluxing aluminum-based brazing filler metal comprises the following raw materials in percentage by weight:
4-8% of soldering flux, 4-20% of Si and the balance of Al, wherein the self-soldering aluminum-based brazing filler metal has the oxygen content of less than 450ppm and the relative density of more than 95%.
The invention is further illustrated and described below in the specification of the invention, where all numerical percent units are weight percent units unless otherwise expressly specified.
In the specification, the term "brazing flux Al-Si alloy composite powder" means that the brazing flux completely coats the Al-Si alloy powder, and the Al-Si alloy powder is completely isolated from oxygen in the environment due to the brazing flux coating layer, so that the oxygen content of the brazing flux Al-Si alloy composite powder is lower than 300ppm, and the excellent brazing performance of the self-brazing aluminum-based brazing filler metal is obtained.
Compared with the prior art, the invention has the beneficial effects that:
the self-brazing aluminum-based brazing filler metal prepared by the method has wide adjustable range of the brazing flux and the Si content, and can meet various brazing and/or welding processes of aluminum alloy such as flame brazing, induction brazing, dip brazing, furnace brazing and the like; the self-brazing aluminum-based brazing filler metal has good ductility, so that the self-brazing aluminum-based brazing filler metal can be further rolled, extruded, drawn and the like, various self-brazing aluminum-based brazing filler metals in the shapes of plates, sheets, wires, foils, rings or special shapes can be economically manufactured, and necessary guarantee is provided for low-cost, reliable and high-strength brazing of a brazing technology. The method has simple and flexible process, and is suitable for mass production and small-batch customization.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.
The invention provides a self-fluxing aluminum-based brazing filler metal and a preparation method thereof, wherein the preparation method comprises the following steps:
a preparation method of self-brazing aluminum-based brazing filler metal comprises the following steps:
step 1: preparing a first aluminum brazing filler metal, wherein the brazing filler metal is brazing flux-clad Al-Si alloy composite powder, and the composite powder specifically comprises the following components in percentage by weight:
4.5-8.5% of a brazing flux, 0-5% of Si with a grain size of 10 μm, and the balance Al;
step 2: preparing a second aluminum brazing filler metal, wherein the brazing filler metal is Al-Si alloy powder, and the alloy powder specifically comprises the following components in percentage by weight:
30-60% of Si and the balance of AL, the Si grain size being 10 μm;
and step 3: and (3) in the ratio of the first aluminum brazing filler metal to the second aluminum brazing filler metal of 75-97.5:2.5-25, mixing the powder according to the requirements of the raw material components;
and 4, step 4: carrying out hot isostatic pressing on the mixed powder by vacuumizing the envelope;
and 5: peeling and machining to obtain the finished product, thus obtaining the self-fluxing aluminum solder.
Also provides a self-brazing aluminum-based brazing filler metal prepared by the method:
a self-fluxing aluminum-based brazing filler metal comprises the following raw materials in percentage by weight:
4-8% of soldering flux, 4-20% of Si and the balance of Al, wherein the oxygen content is less than 450ppm, and the relative density is more than 95%.
In the examples of the present application, the flux used in the examples is K 3 AlF 4 According to the component requirements, the flux can also use fluorine-based flux, and specifically comprises the following components: the method comprises the following steps: k 2 AlF 5 、K 2 AlF 5 ·H 2 O、K 3 AlF 6 、AlF 3 、KZnF 3 、K 2 SiF 6 、Cs 3 AlF 6 、CsAlF 4 ·2H 2 O or Cs 2 AlF 5 .H 2 O；
Or, the chlorine-based brazing flux specifically comprises: naCl, KCl, liCl or ZnCl 2 ；
Or a combination of fluorine-based brazing flux and chlorine-based brazing flux, specifically the two types of brazing flux are used in combination.
It should be further specifically noted that, in the present application, the brazing flux exists in a form of coating Al-Si alloy powder, and in the preparation steps of the present application, the brazing flux can be incorporated into a mixture of the first aluminum brazing filler metal and the second aluminum brazing filler metal in a single brazing flux powder form to produce the required self-brazing aluminum-based brazing filler metal as required;
further, the mixture is composed of the first and second aluminum solders mixed, but in the preparation step of the present invention, a third component can be added, in which: the third component comprises Al-12.6Si eutectic alloy powder which is used for increasing the migration of elements and the flowing of brazing filler metal;
cu, zn or Cu-Zn alloy powder for increasing the constituent liquid phase fraction and improving corrosion resistance.
Example one
Step 1: the first aluminum brazing filler metal is prepared by the following steps:
melting Al-Si alloy in a melting furnace at 780 ℃;
transferring to a tundish, and enabling the molten alloy to flow out of a hole at the bottom of the tundish to form a molten alloy flow beam to enter an atomization chamber protected by N2 atmosphere;
nitrogen is sprayed to convert the melt alloy flow beam into aluminum alloy atomized liquid drops;
the atomized liquid drops enter a brazing flux powder fluidized bed with the granularity of 20 mu m, and the brazing flux is coated with the brazing flux under the inert atmosphere;
and cooling to obtain the first aluminum brazing filler metal composite powder.
In the present example, the content of the first aluminum brazing filler metal was 8%, the particle size of the first aluminum brazing filler metal was 300 μm or less, and the oxygen content was 300ppm or less.
In the step 2: the step flow of preparing the second aluminum brazing filler metal is as follows:
melting Al-40Si alloy in a melting furnace at a temperature of 850 ℃;
transferring to a tundish, and enabling the molten alloy to flow out of a hole at the bottom of the tundish to form a molten alloy flow beam to enter an atomization chamber protected by N2 atmosphere;
injecting nitrogen to convert the melt alloy flow beam into atomized liquid drops of the aluminum alloy;
and cooling to obtain second aluminum brazing filler metal alloy powder.
Wherein the particle size of the second aluminum brazing filler metal is 400 [ mu ] m or less, and the oxygen content is 400ppm or less.
And step 3: the powder mixing step flow is as follows: and (2) putting the first aluminum solder and the second aluminum solder into a double-cone mixer according to the proportion of 80.
And 4, step 4: the process of vacuumizing the envelope and hot isostatic pressing comprises the following steps: putting the prepared mixed powder into an aluminum sheath, and vacuumizing the sheath at 350 ℃ under the condition that the vacuum degree is lower than 1 x 10 < -3 > Pa;
hot isostatic pressing is carried out at the temperature of 450 ℃ and the pressure of 180MPa for 4 hours to obtain a self-fluxing aluminum-based brazing filler metal blank.
And 5: peeling, obtaining a billet of the self-brazing aluminum-based brazing filler metal by machining, and further preparing the self-brazing aluminum-based brazing filler metal into a plate, a sheet, a wire, a foil, a ring or a special-shaped self-brazing aluminum-based brazing filler metal from the self-brazing aluminum-based brazing filler metal, wherein:
the self-brazing aluminum-based brazing filler metal prepared by the steps comprises the following steps: 6.4% of flux K 3 AlF 4 Total 10.2% by weight of Si and the balance of Al;
the relative density of the self-brazing aluminum-based brazing filler metal is 97% (relative to the true density), the oxygen content is 500ppm or less, and the Si grain size is about 10 μm.
Example two
In contrast to example one, the only first braze used was 5%K 3 AlF 4 +95% of Al-1Si alloy composite powder;
the second aluminum brazing filler metal is Al-30Si alloy powder;
the ratio of the first aluminum brazing filler metal to the second aluminum brazing filler metal is 85:
the prepared self-brazing aluminum-based brazing filler metal comprises the following steps: 4.25% of K 3 AlF 4 5.31% Si and the remainder Al;
the relative density of the self-brazing aluminum-based brazing filler metal is 98.5% (relative to the true density), the oxygen content is below 400ppm, the Si grain size is about 10 mu m, and the rest are the same.
EXAMPLE III
In contrast to example one, the only first braze used was 8%K 3 AlF 4 +92% of an Al-5Si alloy composite powder;
the second aluminum brazing filler metal is 4%K 3 AlF 4 +96% of Al-60Si alloy composite powder;
the ratio of the first aluminum brazing filler metal to the second aluminum brazing filler metal is 90:
the prepared self-brazing aluminum-based brazing filler metal comprises the following steps: 7.6% of K 3 AlF 4 10.36% of Si, the remainder being Al;
the relative density of the self-brazing aluminum-based brazing filler metal reaches 96 percent (relative to the true density), the oxygen content is below 400ppm, the Si grain size is about 10 mu m, and the rest are the same.
Example four
Same as the first embodimentIn contrast, the first braze material used alone was 7%K 3 AlF 4 +93% by weight of the Al-4Si alloy composite powder;
the second aluminum brazing filler metal is Al-30 Si-10 Cu alloy powder;
the ratio of the first aluminum brazing filler metal to the second aluminum brazing filler metal is 85:
the prepared self-brazing aluminum-based brazing filler metal comprises the following steps: 5.95% of K 3 AlF 4 7.66% Si, 1.5% Cu, the remainder Al;
the relative density of the self-brazing aluminum-based brazing filler metal reaches 97 percent (relative to the true density), the oxygen content is below 400ppm, the Si grain size is about 10 mu m, and the rest is the same.
EXAMPLE five
In contrast to example one, the only first braze used was 6%K 3 AlF 4 +94% of Al-4Si alloy composite powder;
the second aluminum brazing filler metal is Al-30 Si-8 Zn alloy powder;
the proportion of the first aluminum brazing filler metal to the second aluminum brazing filler metal is 85, the Si grain size is about 10 mu m, wherein:
the prepared self-brazing aluminum-based brazing filler metal comprises the following steps: 4.8% of K 3 AlF 4 9.01% Si, 1.5% Zn, the remainder Al;
the relative density of the self-brazing aluminum-based brazing filler metal reaches 96.8 percent (relative to the true density), the oxygen content is below 400ppm, the Si grain size is about 10 mu m, and the rest are the same.
In order to better understand the technical scheme of the invention, the following is further explained by combining experiments.
Comparative example 1
In contrast to example one, the only first braze used was 2%K 3 AlF 4 +98% of Al-8Si alloy composite powder;
the relative density of the self-brazing aluminum-based brazing filler metal is 95.4% (relative to the true density), the oxygen content is less than 300ppm, the Si grain size is about 10 mu m, and the rest are the same.
Comparative example 2
In contrast to example one, the only first braze used was 5%K 3 AlF 4 +95% of Al-8Si alloy composite powder;
the relative density of the self-fluxing aluminum-based brazing filler metal reaches 95.4 percent (relative to the true density), the oxygen content is below 300ppm, the Si grain size is about 10 mu m, and the rest are the same.
Comparative example 3
Compared with the two phases of the examples, the first brazing filler metal used only is 5%K 3 AlF 4 +95% of Al-1% by weight of the Si alloy composite powder;
the second aluminum brazing filler metal is Al-30% Si alloy powder;
except that the proportion of the first aluminum brazing filler metal to the second aluminum brazing filler metal is 70:
the prepared self-brazing aluminum-based brazing filler metal comprises the following steps: 3.5% of K 3 AlF 4 9.6% of Si, the remainder of Al; the relative density of the brazing filler metal based on aluminum is 98.5% (relative to the true density), the oxygen content is below 420ppm, the Si grain size is about 10 μm, and the rest are the same.
The following experiments were carried out for each of the above examples 1 to 5 and comparative examples 1 to 3:
the solder spreadability is measured by GB11364-89 solder spreadability and joint filling test method to determine the soldering performance. The test plate for the experiment is an 1100 aluminum alloy plate (the size is 40mm multiplied by 5 mm), the block shape of the self-brazing aluminum-based brazing filler metal is used, the mass is 0.2 +/-1%g, the heating speed is 10-15 ℃/min, the brazing temperature is 600 +/-5 ℃, the heat preservation time is 5min, and the actual spreading area of the brazing filler metal is calculated according to the following formula:
actual spread area of solder = actual area of test panel × area of solder measured/area of test panel measured (mm 2)
The result is that the spreading area of the solder is measured to determine the solderability, the larger the area is, the better the solder activity is, the better the solderability is, and the result is the average value of three experiments. In the above experiment, the spreading area of more than 500mm2 is evaluated as "excellent"; 400-500mm2 was rated "good"; 250-400mm2 rated "normal"; the evaluation was "poor" below 250mm2, and the results of the spreadability test of each of examples 1 to 5 and comparative examples 1 to 3 above are shown in Table 1 below.
GB/T228.1-2010' metallic material tensile test first part: room temperature test method "measures the elongation to determine subsequent processability (e.g., extrusion, rolling, stretching, etc.). Three sheets of 50mm (length) × 12.5mm (width) × 1mm (thickness) were cut out from the aluminum-based brazing filler metal obtained in each example, and a tensile test was conducted on an "electronic universal tester" to measure the elongation after fracture, which was calculated according to the following formula:
elongation after fracture = (gauge length after fracture-original gauge length) ÷ original gauge length × 100%
The results determine the subsequent processability in terms of elongation after fracture, for example (such as extrusion, rolling, stretching, etc.), the higher elongation after fracture indicating the better processability, and the above experiments, the elongation after fracture reaching more than 15%, evaluated as "excellent"; 10-15% was rated "good"; 7-10% was rated "normal"; the evaluation of 7% or less was "poor", and the results of elongation after break of each of examples 1 to 5 and comparative examples 1 to 3 are shown in Table 1 below.
The above two indexes were evaluated in total, and the results are shown in Table 1 below.
The results show that the self-brazing aluminum-based brazing filler metal prepared by the method has good brazing activity, at least has subsequent processing performance (such as extrusion, rolling, stretching and the like), meets the requirements of further rolling, extrusion, wire drawing and the like, and can be used for economically preparing various self-brazing aluminum-based brazing fillers of plates, sheets, wires, foils, rings or special shapes or used as self-brazing agent brazing filler metal coating materials of synthetic aluminum alloy composite plates to meet various brazing and/or welding processes of aluminum alloys such as flame brazing, induction brazing, dip brazing, furnace brazing and the like.
The results of the examples outside the scope of the invention show that either the brazing activity is not satisfied or the subsequent processing capability is not available.
Having thus described the invention in detail, it will be apparent that variations and modifications can be effected by one skilled in the art without departing from the spirit and scope of the invention, which will be within the scope of the appended claims.
For more detailed description, the invention also provides application of the self-brazing aluminum-based brazing filler metal in brazing.
The application of the self-brazing aluminum-based brazing filler metal in brazing is as follows:
during brazing, firstly, the brazing flux is melted;
as the temperature is increased to be higher than the solidus temperature of the Al-Si alloy, the Al-Si alloy is initially melted and generates a small amount of liquid phase fraction, because the first aluminum brazing filler metal (the Si content is far lower than 12.6%) and the second aluminum brazing filler metal (the Si content is far higher than 12.6%) are adopted in the invention, the Si gradient difference exists between the two brazing filler metals, the Si mutual diffusion and mutual dissolution of the liquid phase alloy are rapidly triggered, namely the high-concentration Si is diffused and migrated to the low-concentration Si, the Si content is promoted towards the eutectic alloy Si content (12.6 percent Si), and when the Al-12.6Si eutectic composition is crossed, the full liquid phase of the Al-Si eutectic is generated;
with mutual solution propulsion of Si, continuously generated Al-Si eutectic liquid phase continuously propagates and propels towards the first aluminum solder (low Si) by taking the second aluminum solder (high Si) as a center; and together with the molten flux, promote the liquefaction and flow of the whole self-fluxing aluminum solder.
Because the invention adopts the rapid cooling process, the primary Si crystal grains in the self-brazing aluminum-based brazing filler metal are fine and uniform, the size is about 10 mu m, the melting zone is narrow and the melting point is low (compared with the material which is not subjected to the rapid cooling process), the instant melting effect can be achieved, and the brazing mechanism is promoted to be carried out.
Compared with the conventional brazing technology that the brazing filler metal adopts single silicon-aluminum alloy, no matter the content of Si is higher or lower than the eutectic point by 12.6 percent Si, the liquid phase fraction of Al-Si alloy melting during brazing is mainly determined by temperature/time, and the phenomenon of liquid phase diffusion Si among the brazing filler metals is avoided.
The first aluminum brazing filler metal is made of Al-Si alloy composite powder wrapped by brazing flux, the second aluminum brazing filler metal is made of Al-Si alloy powder with high Si content, the first aluminum brazing filler metal and the second aluminum brazing filler metal have the characteristic of low oxygen content, the first aluminum brazing filler metal and the second aluminum brazing filler metal are combined to enable the self-brazing aluminum-based brazing filler metal to be low in oxygen content, the self-brazing aluminum-based brazing filler metal can substantially reduce the brazing flux content, good brazing activity is obtained, good brazing joints are obtained, and cost is saved.
The self-brazing aluminum-based brazing filler metal takes the first aluminum brazing filler metal as a main component (more than 75 percent), so that the self-brazing aluminum-based brazing filler metal has good plasticity/ductility, further rolling, extrusion, wire drawing and the like are met, various self-brazing aluminum-based brazing filler metals of plates, sheets, wires, foils, rings or special shapes are economically manufactured, or the self-brazing aluminum-based brazing filler metal is used as a self-brazing filler metal coating material for synthesizing aluminum alloy composite plates, and the self-brazing aluminum-based brazing filler metal can be met in various brazing and/or welding processes of aluminum alloys such as flame brazing, induction brazing, dip brazing, furnace brazing and the like.
The self-brazing aluminum-based brazing filler metal produced by the method reduces the manufacturing cost due to high utilization rate of raw materials and has the production potential of large-size raw materials.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.
Claims (8)
1. A preparation method of self-brazing aluminum-based brazing filler metal is characterized by comprising the following steps:
step 1: preparing a first aluminum brazing filler metal, wherein the brazing filler metal is brazing flux-clad Al-Si alloy composite powder, and the composite powder specifically comprises the following components in percentage by weight:
4.5-8.5% of flux, 0-5% of Si and the balance of Al, wherein the grain size of Si is 10 mu m;
step 2: preparing a second aluminum brazing filler metal, wherein the brazing filler metal is Al-Si alloy powder, and the alloy powder specifically comprises the following components in percentage by weight:
30-60% Si and balance AL, the Si grain size being 10 μm;
and 3, step 3: and when the ratio of the first aluminum brazing filler metal to the second aluminum brazing filler metal is 75-97.5:2.5-25, mixing the powder according to the requirements of the raw material components;
and 4, step 4: carrying out hot isostatic pressing on the mixed powder by vacuumizing the envelope;
and 5: peeling and machining to obtain the finished product, thus obtaining the self-fluxing aluminum solder.
2. The method for producing a self-fluxing aluminum-based solder according to claim 1, wherein the flux is a fluorine-based flux, a chlorine-based flux or a combination of a fluorine-based flux and a chlorine-based flux, wherein:
a fluorine-based flux comprising: k 3 AlF 4 、K 2 AlF 5 、K 2 AlF 5 ·H 2 O、K 3 AlF 6 、AlF 3 、KZnF 3 、K 2 SiF 6 、Cs 3 AlF 6 、CsAlF 4 ·2H 2 O or Cs 2 AlF 5 .H 2 O；
A chlorine-based flux comprising: naCl, KCl, liCl or ZnCl 2 。
3. The method for preparing a self-fluxing aluminum-based solder according to claim 2, wherein in the step 1, the step flow of preparing the first aluminum solder is as follows:
melting Al-Si alloy in a melting furnace at 780 ℃;
transferring to a tundish, and enabling the molten alloy to flow out of a hole at the bottom of the tundish to form a molten alloy flow beam to enter an atomization chamber protected by N2 atmosphere;
injecting nitrogen to convert the melt alloy flow beam into aluminum alloy atomized liquid drops;
the atomized liquid drops enter a brazing flux powder fluidized bed with the granularity of 20 mu m, and the brazing flux is coated with the brazing flux under the inert atmosphere;
and cooling to obtain the first aluminum brazing filler metal composite powder.
4. The method for preparing a self-fluxing aluminum-based solder according to claim 3, wherein in the step 2, the step flow for preparing the second aluminum solder is as follows:
melting Al-40Si alloy in a melting furnace at a temperature of 850 ℃;
transferring the alloy to a tundish, and enabling the alloy to flow out from a hole at the bottom of the tundish to form a melt alloy flow beam to enter an atomization chamber protected by N2 atmosphere;
injecting nitrogen to convert the melt alloy flow beam into atomized liquid drops of the aluminum alloy;
and cooling to obtain second aluminum brazing filler metal alloy powder.
5. The method for preparing a self-fluxing aluminum-based solder according to claim 4, wherein in the step 3, the step flow of powder mixing is as follows: and (2) putting the first aluminum brazing filler metal and the second aluminum brazing filler metal into a double-cone mixer according to the proportion of 80.
6. The method for preparing a self-fluxing aluminum-based brazing filler metal according to claim 5, wherein in the step 4, the steps of vacuumizing the envelope and hot isostatic pressing are as follows: putting the prepared mixed powder into an aluminum sheath, and vacuumizing the sheath at 350 ℃ under the condition that the vacuum degree is lower than 1 x 10 < -3 > Pa;
hot isostatic pressing is carried out at the temperature of 450 ℃ and the pressure of 180MPa for 4 hours to obtain a self-fluxing aluminum-based brazing filler metal blank.
7. The method for producing a self-brazing aluminum-based brazing filler metal according to claim 1, wherein in the step 5, the self-brazing aluminum-based brazing filler metal is formed into a plate, a sheet, a wire, a foil, a ring or a shaped self-brazing aluminum-based brazing filler metal.
8. A self-fluxing aluminum-based solder prepared by the method of any one of claims 1 to 7, characterized by comprising the following raw materials by weight percent:
4-8% of soldering flux, 4-20% of Si and the balance of Al;
wherein, the oxygen content of the self-brazing aluminum-based brazing filler metal is less than 450ppm, and the relative density is more than 95 percent.
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