WO2023246018A1 - High-corrosion-resistance collecting tube material, and preparation method therefor and use thereof - Google Patents

Abstract

A high-corrosion-resistance collecting tube material, and a preparation method therefor and a use thereof. The high-corrosion-resistance collecting tube material is formed by compounding an outer-layer alloy and a core-layer alloy. The outer-layer alloy comprises the following components in percentage by mass: silicon: 9.0-11.0%, iron: 0.05-0.25%, copper: ≤0.1%, manganese: ≤0.05%, magnesium: ≤0.03%, zinc: 1.2-1.3%, and titanium: ≤0.1%; and the total proportion of other impurities is not greater than 0.15%, with the balance being aluminum. The core-layer alloy comprises the following components in percentage by mass: silicon: 0.05-0.12%, iron: 0.05-0.18%, copper: 0.25-0.4%, manganese: 1.0-1.5%, magnesium: ≤0.03%, zinc: ≤0.1%, and titanium: 0.08-0.15%; and the total proportion of other impurities is not greater than 0.15%, with the balance being aluminum. The corrosion resistance of the collecting tube material is greatly improved by means of the content of the specific metal components in the outer-layer alloy and the core-layer alloy. After brazing, brazing strength is high, and corrosion resistance is excellent.

Description

A highly corrosion-resistant header pipe material and its preparation method and application Technical field

The present invention relates to the technical field of alloys for heat exchangers, and more specifically, to a highly corrosion-resistant header pipe material and its preparation method and application.

Background technique

The parallel flow heat exchanger is assembled with surface-sprayed zinc extruded porous tubes (MPE tubes for short), composite fin foils, high-frequency welded headers, plugs, side plates, etc., and operates at a temperature of 590 to 605°C. Brazed down. Through brazing, the brazing material on the surface of the header, composite fin foil, and plug cap melts and flows, and after cooling, is connected with the MPE pipe to form a whole.

Usually the collector pipe material is composed of an outer layer alloy and a core layer alloy. The composition of the outer layer alloy is 4XXX series aluminum alloy + 1wt.% Zn. Its main purpose is to use zinc element to effectively reduce the aluminum alloy electrode potential and give priority to be corroded, thereby protecting the core layer of the header pipe from being corroded and perforated preferentially, thereby extending the service life of the condenser.

The corrosion resistance of the collecting pipe material directly affects the overall service life of the condenser. However, with the high-temperature brazing process, the solder melts and flows, which easily causes the thickness of the solder to decrease. At the same time, as heat exchangers develop in the direction of miniaturization and lightweight, the thickness of collector pipe materials has also shown a trend of thinning, which has also put forward higher requirements for the pressure resistance and corrosion resistance performance indicators of collector pipe materials.

In particular, commercial air-conditioning condensers have higher requirements for corrosion resistance than small automotive air-conditioning condensers due to their large size, large cooling capacity, high working pressure, and harsher operating environment. In order to reduce the cost of small air-conditioning condensers for vehicles, some manufacturers have begun to use lower-cost MPE tubes with silicon and zinc layers (referred to as SiZnFlux extruded porous tubes. The surface silicon layer melts during brazing and can act as a brazing material)+ For the combination of light fins and ordinary headers, since the corrosion resistance of SiZnFlux extruded porous tubes is not as good as that of MPE tubes with only zinc layers, they cannot meet the corrosion resistance requirements of commercial air conditioning condensers. Therefore, commercial air conditioning condensers can only be used at a slightly higher cost. The MPE pipe with only zinc layer (also called ZnFlux extruded porous pipe) + composite fin + collector pipe combination. As the thickness of the collector pipe material continues to become thinner, the traditional common collector pipe material is difficult to meet the condensation requirements of commercial air conditioners. The SWAAT corrosion test requires that the device does not perforate for a long time.

Therefore, there is a need to develop a highly corrosion-resistant header pipe material for commercial air-conditioning condensers with better corrosion resistance.

Contents of the invention

In order to overcome the defect of poor corrosion performance described in the above-mentioned prior art, the present invention provides a highly corrosion-resistant collector pipe material. Through the specific metal component content in the outer layer alloy and the core layer alloy, the collector pipe material The corrosion resistance is greatly improved; after brazing, the brazing strength is high and the corrosion resistance is excellent.

Another object of the present invention is to provide a method for preparing the highly corrosion-resistant header pipe material used in the above-mentioned commercial air-conditioning condenser.

Another object of the present invention is to provide the application of the above-mentioned highly corrosion-resistant header pipe material for commercial air-conditioning condensers.

In order to solve the above technical problems, the technical solution adopted by the present invention is:

A highly corrosion-resistant collector pipe material, which is composed of an outer layer alloy and a core layer alloy. It is characterized in that the outer layer alloy includes the following mass percentage components: silicon: 9.0 to 11.0%, iron: 0.05 ~0.25%, copper: ≤0.1%, manganese: ≤0.05%, magnesium: ≤0.03%, zinc: 1.2~1.3%, titanium: ≤0.1%; the total proportion of other impurities is not greater than 0.15%, the balance of aluminum;

The core layer alloy includes the following mass percentage components: silicon: 0.05~0.12%, iron: 0.05~0.18%, copper: 0.25~0.4%, manganese: 1.0~1.5%, magnesium: ≤0.03%, zinc: ≤ 0.1%, titanium: 0.08~0.15%; the total proportion of other impurities is not more than 0.15%, the balance is aluminum.

In the outer alloy, the silicon content is 9 to 11%, which makes the overall melting point of the outer alloy lower, meeting the brazing requirements, and can be used in the brazing process of commercial air-conditioning condensers.

The zinc content in the outer layer alloy is increased from the conventional 1.0% to 1.2~1.3%, and the copper content in the core alloy is increased from 0.05~0.20% in the traditional 3003 alloy to 0.25~0.4%, further improving the outer layer and The potential difference in the core layer allows the outer 4XXX brazing layer alloy to form a better sacrificial anode protection effect on the 3XXX core layer alloy. In the early stage of corrosion, the outer alloy layer forms lamellar corrosion, and the core layer will not be corroded preferentially, extending the service life of the collector pipe material. At the same time, the copper element in the core material alloy can also improve the post-brazing strength of the collector pipe material, and the thickness of the collector pipe material can be further reduced.

The zinc content in the outer alloy is controlled to be 1.2 to 1.3%. The inventor's research found that if the zinc content drops below 1.2%, when brazing at 600°C, the zinc will flow with the molten outer alloy brazing material to the welding corners, etc., resulting in the total amount of zinc remaining in the outer layer of the header after brazing. A large reduction, the potential difference between the core layer alloy and the core layer alloy is greatly reduced, and the sacrificial anode cannot effectively protect the core layer; if the zinc content exceeds 1.3%, the zinc will flow to the header along with the molten outer alloy solder. The total amount of zinc at the welding angle with the MPE pipe will also be relatively large, which will cause the electrode potential at the welding angle to be relatively low, which will easily lead to preferential corrosion and lead to condenser leakage.

The iron content in the outer alloy is controlled to be 0.05 to 0.25%. The inventor's research found that if the iron content exceeds 0.25%, it is easy to form a large amount of Al-Fe-Si phase rich in iron and silicon with silicon. A local galvanic reaction is formed between the Al-Fe-Si phase and aluminum, causing the area to be blocked. It is corroded away preferentially to form pitting corrosion, thereby reducing the corrosion resistance of the alloy; since the raw material used for aluminum alloys is 99.7% ordinary aluminum ingots, there are inevitably elements such as iron and silicon. If the iron content drops below 0.05%, the production cost will increase. Too high.

The magnesium content in the outer alloy is controlled to be ≤0.03%. If the magnesium content exceeds 0.03%, magnesium will evaporate during high-temperature brazing and chemically react with the flux (main component is KFAl ₄ ) during nitrogen shielded welding, which may easily cause poor brazing.

Through the synergistic effect of the proportions of the components in the outer layer alloy, it plays a fundamental supporting role in improving the overall corrosion resistance of the commercial air conditioning condenser.

Preferably, in the outer layer alloy, the individual mass percentage of other impurity elements is ≤0.05%.

Preferably, the outer layer alloy includes the following mass percentage components: silicon: 9.53~10.47%, iron: 0.06~0.24%, copper: ≤0.05%, manganese: ≤0.04%, magnesium: ≤0.02%, zinc: 1.21～1.28%, titanium: ≤0.04%; the total proportion of other impurities is not more than 0.15%, the balance is aluminum.

More preferably, the outer layer alloy includes the following mass percentage components: silicon: 10.01~10.47%, iron: 0.09~0.2%, copper: ≤0.05%, manganese: ≤0.04%, magnesium: ≤0.02%, zinc : 1.22～1.26%, titanium: ≤0.04%; the total proportion of other impurities is not more than 0.15%, the balance of aluminum.

In order to obtain fine recrystallized grains and good formability of traditional 3003 alloy, the iron-silicon ratio is usually designed at a ratio of about 3:1, and the silicon content and iron content are usually about 0.15 to 0.25% and 0.45 to 0.65% respectively. High content control. When the silicon and iron content are high, when the outer alloy layer is corroded away, the corrosion will enter the 3003 core layer, and the corrosion rate of the core layer will accelerate. In the core layer alloy of the present invention, the silicon content and iron content are reduced to 0.05-0.12% and 0.05-0.18% respectively. By adopting a low-silicon and low-iron design, when corrosion enters the core layer alloy, the corrosion rate of the core layer will be greatly slowed down, thereby further extending the service life of the header material. Silicon and iron are inevitable impurity elements in 3XXX aluminum alloys. If the silicon or iron content drops below 0.05%, high-purity aluminum ingot raw materials must be used for smelting, and the production cost is high.

In addition, the low silicon content in the core layer alloy and the high silicon content in the outer 4XXX brazing layer alloy will further increase the concentration difference, which is conducive to the formation of Brownian precipitation zones in the core layer near the outer layer interface. Brownian precipitation The charged electrode potential is lower than that of the center of the 3XXX core layer and exhibits lamellar corrosion. It can also function as a sacrificial anode to protect the center of the core layer, thereby further increasing the service life of the collector pipe material. If the silicon content exceeds 0.12% or the iron content exceeds 0.18%, on the one hand, the corrosion resistance of the core layer alloy itself will become worse, which is not conducive to the formation of large grains after high-temperature brazing; on the other hand, the silicon concentration of the core layer alloy and the outer layer alloy will vary. If the difference is not large enough, Brownian precipitation bands will not easily form in the area near the interface of the core layer alloy close to the outer layer alloy, and the sacrificial anode protection effect on the center of the core layer will also be weakened.

The copper content in the core layer alloy is controlled to 0.25-0.4%. The inventor's research found that copper can significantly improve the strength and electrode potential of aluminum alloys. If the copper content drops below 0.25%, on the one hand, the strength of the core alloy after brazing will be relatively low, and on the other hand, the electrode potential of the core alloy will not be high enough, and the If the potential difference of the outer alloy is not large enough, the sacrificial anode protection effect of the outer alloy on the core alloy will be weakened; if the copper content exceeds 0.4%, the strength of the core alloy will be too high, and the formability will become worse, which is not conducive to high-frequency welding. Pipe making.

Control the manganese content in the core layer alloy to 1.0-1.5%; manganese can significantly improve the strength of 3XXX aluminum alloy. Manganese and aluminum form MnAl ₆ compound dispersion particles to prevent the recrystallization process of the aluminum alloy, which can improve the material's high-temperature sagging resistance. Another function of MnAl ₆ is to dissolve iron and form (Fe,Mn)Al ₆ to reduce the harmful effects of iron; if the manganese content drops below 1.0%, the formed (Fe,Mn)Al ₆ and MnAl ₆ compounds will disperse There are few particles, which cannot fully hinder the recrystallization process during high-temperature brazing, and the high-temperature anti-sag performance of the material will be significantly reduced; if the manganese content exceeds 1.5%, the solid solution of manganese in the aluminum matrix is too large (658°C The maximum solubility of manganese in aluminum is 1.82%), if the strength of the core layer alloy is too high, the formability will become worse, which is not conducive to high-frequency welding pipe making; at the same time, the matrix resistance will increase, the electrical conductivity will decrease, and the corresponding thermal conductivity will also decrease.

The magnesium content in the core layer alloy is controlled to be ≤0.03%; if the magnesium content exceeds 0.03%, magnesium will evaporate during high-temperature brazing and chemically react with the flux (main component is KFAl ₄ ) during nitrogen shielded welding, causing Poor brazing.

The titanium content in the core layer alloy is controlled to 0.08-0.15%; titanium can not only play a role in grain refinement in aluminum alloys, but also form peritectics in the aluminum matrix, showing lamellar corrosion characteristics, which can improve the corrosion resistance of aluminum alloys. ; If the titanium content is less than 0.08%, titanium will not easily form peritectes in the aluminum matrix, and cannot achieve the effect of lamellar corrosion to improve corrosion resistance; if the titanium content exceeds 0.15%, titanium will easily form coarse compounds with elements such as manganese, causing The formability of the material decreases.

Preferably, the core layer alloy includes the following mass percentage components: silicon: 0.06~0.11%, iron: 0.08~0.17%, copper: 0.26~0.38%, manganese: 1.04~1.45%, magnesium: ≤0.02%, Zinc: ≤0.04%, titanium: 0.09~0.14%; the total proportion of other impurities is not more than 0.15%, and the balance is aluminum.

More preferably, the core layer alloy includes the following mass percentage components: silicon: 0.07~0.10%, iron: 0.10~0.15%, copper: 0.28~0.34%, manganese: 1.15~1.36%, magnesium: ≤0.02% , Zinc: ≤0.04%, Titanium: 0.1~0.12%; the total proportion of other impurities is not more than 0.15%, and the balance is aluminum.

Preferably, the thickness of the highly corrosion-resistant collecting pipe material is 1.1 to 2.5 mm.

Preferably, the thickness of the outer alloy layer is 3.5% to 13% of the thickness of the highly corrosion-resistant collector pipe material.

If the thickness of the outer alloy is within this ratio, the solder on one side of the collector pipe material can be connected to the MPE pipe to form a solid whole after melting. This can not only ensure the thickness of the core layer of the collector pipe material and thereby ensure the overall strength, but also Make sure the brazing is good. When the ratio is higher than this range, on the one hand, the core layer thickness of the collector tube will be insufficient, resulting in insufficient strength. At the same time, there may be excess solder. The excess solder will cause local erosion of the MPE tube and composite fins, thereby reducing the condensation of commercial air conditioners. The overall corrosion resistance of the device; when it is lower than this ratio range, it may cause partial soldering, missing soldering and other poor brazing conditions.

The present invention also protects the preparation method of the above-mentioned highly corrosion-resistant collector pipe material, which includes the following steps:

S1. According to the component content of the outer layer alloy and the core layer alloy, separately prepare the outer layer ingot and the core layer ingot through smelting, refining, degassing, slag removal and casting;

S2. Carry out sawing, milling, heating, hot rolling, and shearing on the outer plate ingot to prepare the outer plate;

Saw and mill the core layer board ingots to obtain core layer board ingots to be welded and assembled;

S3. Stack the cleaned outer plates and the core plate ingots to be welded and assembled, bundle them with steel strips, and undergo heating, hot rolling, cold rolling, intermediate annealing, cold rolling again, cleaning, and slitting. The highly corrosion-resistant collecting pipe material is obtained.

Preferably, the thickness of the outer layer plate ingot is 400-500mm, and the thickness of the core layer plate ingot is 360-500mm.

Preferably, the thickness of the outer plate is 22.5-55 mm.

Preferably, the controlled milling amount of the milling surface is 8-10mm/each surface.

Preferably, the hot rolling composite is to produce a composite strip coil with a thickness of 3.5 to 6 mm.

The invention also protects a collector pipe, which is made from the above-mentioned highly corrosion-resistant collector pipe material through high-frequency welding.

The present invention also protects the application of the above-mentioned header in commercial air-conditioning condensers.

Compared with the prior art, the beneficial effects of the present invention are:

The present invention develops a collecting pipe material with excellent corrosion resistance, which can be used in commercial air-conditioning condensers. Through the specific metal component content in the outer layer alloy and core layer alloy, the corrosion resistance of the header material is greatly improved. After brazing, the brazing strength is high and the corrosion resistance is excellent.

Detailed ways

The present invention will be further described below in conjunction with specific embodiments.

Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in this technical field.

Examples 1 to 5

Embodiments 1 to 5 respectively provide a collector pipe material, which is composed of an outer layer alloy and a core layer alloy. The compositions of the outer layer alloy and core layer alloy are shown in Table 1. The preparation method of the collector pipe material is as follows:

S1. According to the component content of the outer layer alloy and the core layer alloy, prepare respectively, and through smelting, refining, degassing, slag removal and casting, outer layer ingots with a thickness of 400~500mm and thickness of 360~360mm are respectively obtained. 500mm core layer ingot;

Smelting: The smelting temperature is controlled at 740-780°C. After the raw materials are melted, the stirring, slag removal, and component sampling tests are passed, and then the aluminum liquid is poured into the static furnace;

Refining: Use _N2 to refine in a static furnace for 10-12 minutes, then stir, remove slag, and let stand for 5-10 minutes;

Casting: After passing the composition sampling test, the aluminum liquid in the static furnace is degassed and filtered online, and Al-Ti-B wire is used to refine the grains online and cast into slabs.

S2. Carry out sawing, milling, heating, hot rolling, and shearing on the outer plate ingot to obtain an outer plate with a thickness of 22.5 to 55 mm;

The core layer board ingots are sawed, heated and milled to obtain core layer board ingots to be welded and assembled;

The milling surface control milling amount is 8-10mm/each surface;

Heating: The metal temperature is controlled at 480-510℃ and maintained for 1-3 hours;

Hot rolling: multi-pass rolling, final rolling temperature ≥350℃;

Shearing: Cool to 300℃ and start cutting;

Soaking: The temperature of the core plate ingot is controlled at 600-610℃ for 10-15 hours;

S3. Stack the cleaned outer plate and the core plate ingot to be welded and assembled (usually the outer plate is placed on top and the core plate ingot is placed below), bundled with steel strips, heated and hot-rolled to combine. Composite strip coils with a thickness of 3.5 to 6 mm are obtained, and then cold rolled, intermediate annealed, cold rolled again, cleaned, and cut to obtain collector pipe materials;

Heating: The metal temperature is controlled at 480-510℃ and maintained for 1-3 hours;

Hot rolling: multi-pass rolling, the final rolling temperature is controlled at 260-300℃;

Cold rolling: multi-pass rolling, rolling to the intermediate thickness, annealing and cooling, and then rolling to the required finished product thickness.

Intermediate annealing: The metal temperature is controlled at 350-450°C for 2-3 hours;

The thickness of the header material prepared in the embodiment is 1.5 mm, in which the outer layer alloys of embodiments 1 to 5 account for 7.6%, 6.4%, 7.3%, 8.1% and 9.7% respectively.

Table 1 Component composition (wt.%) of the outer layer alloy and core layer alloy of Examples 1 to 5

Comparative Examples 1 to 3

Comparative Examples 1 to 3 respectively provide a collector pipe material, which is composed of an outer layer alloy and a core layer alloy. The compositions of the outer layer alloy and core layer alloy are shown in Table 2. The preparation method of the collector pipe material is the same as that in the embodiment. .

The thickness of the header prepared in the comparative example is 1.5mm, in which the outer layer alloy of comparative examples 1 to 3 accounts for 9.5%, 7.7% and 6.5% respectively.

Table 2 Components of the outer layer alloy and core layer alloy of Comparative Examples 1 to 3 (wt.%)

Performance Testing

Conduct performance testing on the header materials prepared in the above examples and comparative examples. The specific methods are as follows:

Mechanical properties: The tensile strength of the collector pipe materials before and after brazing were tested respectively. The brazing conditions were high-temperature simulated brazing at 600℃×5min. The tensile strength was in accordance with GB/T 228.1-2010 "Metal Materials" Tensile Test Part 1: Room Temperature Test Method" Prepare the sample and conduct the test at room temperature.

Corrosion resistance: For headers made by high-frequency welding, perform high-temperature simulated brazing at 600°C × 5 minutes, and then conduct a SWAAT 700h corrosion test according to ASTM G85-2011 test standards, and then take 20 corrosion points to calculate the average corrosion pit. Depth, the smaller the depth of the corrosion pit, the better the corrosion resistance.

The test results of the examples and comparative examples are shown in Table 3.

Table 3 Test results of Examples and Comparative Examples

According to the test results in Table 3, it can be seen that the collector pipe materials of each embodiment of the present invention have excellent mechanical properties before and after brazing. The tensile strength before brazing is ≥180MPa, and the tensile strength after brazing is ≥130MPa. The tensile strength of the header material of the comparative example after brazing is 112-123MPa, which is much lower than that of the embodiment.

According to the corrosion resistance test results, the header pipes made by high-frequency welding of the header materials of Examples 1 to 5 have good corrosion resistance after brazing. The average corrosion pit depth of the SWAAT 700h corrosion test is ≤0.14mm.

Obviously, the above-mentioned embodiments of the present invention are only examples to clearly illustrate the present invention, and are not intended to limit the implementation of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. An exhaustive list of all implementations is not necessary or possible. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (10)

1. A highly corrosion-resistant collector pipe material, which is composed of an outer layer alloy and a core layer alloy. It is characterized in that the outer layer alloy includes the following mass percentage components: silicon: 9.0 to 11.0%, iron: 0.05 ~0.25%, copper: ≤0.1%, manganese: ≤0.05%, magnesium: ≤0.03%, zinc 1.2~1.3%, titanium ≤0.1%; the total proportion of other impurities is not more than 0.15%, the balance of aluminum;

   The core layer alloy includes the following mass percentage components: silicon: 0.05~0.12%, iron: 0.05~0.18%, copper: 0.25~0.4%, manganese: 1.0~1.5%, magnesium: ≤0.03%, zinc: ≤ 0.1%, titanium: 0.08~0.15%; the total proportion of other impurities is not more than 0.15%, the balance is aluminum.
2. The highly corrosion-resistant collector pipe material according to claim 1, wherein the thickness of the highly corrosion-resistant collector pipe material is 1.1 to 2.5 mm.
3. The high corrosion resistance collector pipe material according to claim 1, characterized in that the thickness of the outer alloy layer is 3.5% to 13% of the thickness of the high corrosion resistance collector pipe material.
4. The high corrosion resistance collecting pipe material according to claim 1, characterized in that the outer layer alloy includes the following mass percentage components: silicon: 9.53~10.47%, iron: 0.06~0.24%, copper: ≤0.05 %, manganese: ≤0.04%, magnesium: ≤0.02%, zinc: 1.21~1.28%, titanium: ≤0.04%; the total proportion of other impurities is not more than 0.15%, the balance of aluminum.
5. The high corrosion resistance collecting pipe material according to claim 1, characterized in that the core layer alloy includes the following mass percentage components: silicon: 0.06~0.11%, iron: 0.08~0.17%, copper: 0.26~ 0.38%, manganese: 1.04~1.45%, magnesium: ≤0.02%, zinc: ≤0.04%, titanium: 0.09~0.14%; the total proportion of other impurities is not greater than 0.15%, and the balance is aluminum.
6. The preparation method of highly corrosion-resistant header pipe material according to any one of claims 1 to 5, characterized in that it includes the following steps:

   S1. According to the component content of the outer layer alloy and the core layer alloy, separately prepare the outer layer ingot and the core layer ingot through smelting, refining, degassing, slag removal and casting;

   S2. Carry out sawing, milling, heating, hot rolling, and shearing on the outer plate ingot to prepare the outer plate;

   The core layer board ingot is sawed, heated and milled to obtain the core layer board ingot to be welded and assembled;

   S3. Stack the cleaned outer plates and the core plate ingots to be welded and assembled, bundle them with steel strips, and undergo heating, hot rolling and compounding, cold rolling, intermediate annealing, cold rolling again, cleaning, and slitting to obtain The highly corrosion-resistant header pipe material.
7. The preparation method according to claim 6, characterized in that the thickness of the outer layer ingot is 400-500 mm, and the thickness of the core layer ingot is 360-500 mm.
8. The preparation method according to claim 6, characterized in that the controlled milling amount of the milling surface is 8-10mm/each surface; the hot-rolled composite is to obtain a composite strip coil with a thickness of 3.5-6mm.
9. A header, characterized in that it is made from the highly corrosion-resistant header material described in any one of claims 1 to 5 through high-frequency welding.
10. Application of the header described in claim 9 in a commercial air conditioning condenser.