WO2018049585A1 - Aluminum alloy composite strip for internal threaded heat exchange tube, and manufacturing method therefor - Google Patents

Abstract

An aluminum alloy composite strip for producing an internal threaded heat exchange tube, and a method for manufacturing the aluminum alloy composite strip. The method comprises the following steps: melting ingots; performing surface treatment; performing composite hot-rolling to obtain a hot-rolled composite strip comprising an external aluminum alloy layer and an internal aluminum alloy layer; performing cold rolling on the composite strip; annealing to obtain a completely softened composite aluminum strip; thread rolling, i.e., rolling threads on the surface of the internal aluminum alloy layer of the softened composite aluminum strip to obtain a threaded composite strip; and slitting the threaded composite strip to obtain a composite strip for manufacturing the heat exchange tube.

Description

Aluminum alloy composite strip for internal thread heat exchange tube and manufacturing method thereof Technical field

The invention relates to the field of heat exchange system materials, in particular to an aluminum alloy composite strip for producing internal thread heat exchange tubes and a manufacturing method thereof.

Background technique

The heat exchanger is formed by connecting heat exchange tubes and aluminum alloy fins. Because of the different connection modes of the heat exchange tube and the aluminum alloy fin, the heat exchanger is divided into direct heat transfer and indirect heat transfer. The indirect heat transfer is that the heat exchange tube and the aluminum alloy fin are connected by a mechanical expansion tube, such as a fin-type evaporator and a condenser of a household air conditioner, and the internal thread copper tube is a main pipeline, and the external aluminum foil fin is expanded. The purpose of such connection is to give full play to the respective characteristic advantages of the copper-aluminum materials and improve the efficiency of the heat exchange component, but the disadvantages of the heat exchange system are particularly obvious: on the one hand, the heat transfer tube and the fin are combined for mechanical contact, heat transfer The efficiency is low, and the fins are very demanding. The fins with deformation or cracking cannot contact the pipe, which greatly reduces the heat exchange efficiency. On the other hand, the mechanical expansion pipe connection method requires very high uniformity of the thickness of the heat exchange pipe wall. If the thickness is not uniform, it is easy to produce defects such as unilateral cracking during the expansion and expansion process, so the application of the indirect heat transfer heat exchange system is greatly limited. The direct heat transfer is that the heat exchange tube and the alloy fins are connected by welding metallurgy. The heat transfer system has compact structure, good metal contact surface, good shock resistance, close contact resistance to zero, and low heat loss. High thermal efficiency and more and more applications.

In terms of materials, aluminum alloy is light and cheap, has good heat dissipation and corrosion resistance, and can adapt to the heat exchanger to develop in the direction of high efficiency, light weight, low cost and low energy consumption, and adopts aluminum alloy heat exchanger instead of copper heat exchanger. Has become the development trend of heat exchangers.

In the structure of the heat exchange tube, the internal threaded tube can increase the heat exchange contact area by 1-3 times compared with the light pipe, and the change of the flow state of the heat transfer medium can improve the heat exchange efficiency by more than 20%, and the internal thread Pipes are getting more and more attention.

At present, the internally-threaded aluminum tube is mostly prepared by drawing method: the aluminum tube is made of a single material aluminum alloy, and the extruded tube blank, multi-pass cold drawing and finally the cold-drawn aluminum alloy threaded pipe on the threaded mold are used. However, at present, the cold drawn internal threaded aluminum tube has the following problems: (1) The aluminum alloy tube of a single material can only be cold drawn into a pattern, and the cold drawn aluminum alloy tube cannot be directly brazed with the fin, and mechanical expansion tube is still needed. The way to connect. (2) Lubricating oil must be used during the drawing process, resulting in environmental pollution and cost increase; at the same time, the metal chips formed by the mandrel cutting, once entering the heat exchange system, may cause unstable use of the heat exchanger. (3) Due to the limitation of the drawing process, the thread structure and the tooth shape prepared by the drawing process are single, which further affects the heat exchange efficiency, and it is difficult to meet the requirements of miniaturization, low cost and high efficiency of the heat exchanger. (4) Since the raw material is a high-precision extruded light pipe, the price is high; in addition, the production efficiency of the internally threaded aluminum pipe is low (<60 m/min), The comprehensive yield is about 70%, resulting in higher comprehensive production costs.

Summary of the invention

In order to solve the above-mentioned defects in the prior art, the present invention provides an aluminum alloy composite strip for internally threaded heat exchange tubes and a method for manufacturing the same, and the aluminum alloy composite strip produced by the method of the present invention produces heat exchange. The internally threaded heat exchange tube can be brazed to the aluminum alloy fins for direct heat transfer.

In order to achieve the above object, the present invention adopts the following technical solutions:

The invention discloses a method for manufacturing an aluminum alloy composite strip for an internally threaded heat exchange tube, and the manufacturing method comprises the following steps:

Smelting and casting into ingots, smelting each of the aluminum alloy raw materials, and casting each of the blank ingots;

Surface treatment, surface milling of each blank ingot to obtain clean ingots of various surfaces;

Composite hot rolling, hot rolling of each surface clean ingot to obtain a hot rolled composite strip comprising an outer layer of aluminum alloy and an inner layer of aluminum alloy;

Cold rolling, the hot rolled composite strip is cold rolled in multiple passes to obtain a cold rolled composite strip;

Annealing, annealing the cold rolled composite strip to obtain a fully softened composite aluminum strip;

Thread rolling, rolling a thread on the inner aluminum alloy surface of the softened composite aluminum strip to obtain a threaded composite strip;

The slitting is performed, and the threaded composite strip is slit to obtain a composite strip for manufacturing a heat exchange tube.

As a preferred embodiment, the weight percentage of each element in the outer aluminum alloy is: Si is 7.0%-12.5%, Zn is 0-1.0%, and the balance is Al and the content of impurities is less than 0.5%. The inner layer aluminum alloy comprises a core material layer, and the weight percentage of each element in the core material layer aluminum alloy is: Mn is 1.0%-1.8%, Cu is 0.1-0.8%, Ti is 0.1-0.25%, and Zr is 0-0.2%, Fe is 0.1-0.3%, and the balance is Al and the content of impurities below 0.15% is unavoidable. The outer aluminum alloy accounts for 5%-15% of the total thickness of the strip.

Alternatively, the inner layer aluminum alloy comprises a core material layer aluminum alloy and an anti-corrosion layer aluminum alloy, the core material layer aluminum alloy is located between the outer layer aluminum alloy and the anti-corrosion layer aluminum alloy; The total thickness of the material is 5-15%.

The weight percentage of each element in the anti-corrosion layer aluminum alloy is: Zn is 0.8-1.3%, Fe is 0.2-0.4%, Si content is less than 0.3%, and the balance is Al and the content of impurities is less than 0.15%.

Specifically, the cold rolled composite strip obtained by the cold rolling step has a thickness of 0.2-1 mm; the annealing step has an annealing temperature of 330-420 ° C, and the holding time is 2-6 h.

In order to reduce the difficulty of welding from the strip to the tube, in the thread rolling step, a rib parallel to the longitudinal direction of the composite strip is rolled on each of the edges of the long sides of the softened composite aluminum strip. The rib height is 0.1-0.2 mm.

In the thread rolling step, the thread obtained by the thread rolling step has a tooth height of 0.2-0.5 mm, a tooth bottom width of 0.2-0.8 mm, a groove bottom width of 0.2-1.0 mm, and a apex angle of 30-60°, the thread rotation angle is 0-45°, and the number of threads is 40-80, the heat exchange tube produced has better heat exchange effect.

Specifically, in the thread rolling step, two or more sets of embossing machines are used for embossing, and the threads on the obtained threaded plate are crossed threads.

The invention also discloses an aluminum alloy composite strip for internal thread heat exchange tubes, which is obtained by any of the above methods.

Compared with the prior art, the present invention has the following beneficial effects:

1. The heat exchanger internal thread heat exchange tube manufactured by using the aluminum alloy composite strip of the invention can replace the copper heat exchange tube, and meets the requirements of miniaturization, light weight, high heat exchange efficiency and low cost of the heat exchanger.

2. The heat transfer efficiency of the heat exchange tubes prepared by the invention is greatly improved. On the one hand, the leather material and the fin of the aluminum alloy composite strip are metallurgically connected by brazing, the contact thermal resistance is low, and the heat transfer efficiency is high; on the other hand, the different tooth profiles and layout threads of the core material are rolled, The contact area with the heat transfer medium is large, thereby further improving the heat exchange efficiency.

3. Realize the diversified thread structure and tooth shape of the composite strip of heat exchange tube. Operators use different thread rolling processes to roll a variety of thread forms, such as parallel single threads, angled single threads, cross angle threads, and different thread widths and heights. Through the structure and tooth profile adjustment of the thread, the heat transfer medium is turbulent in the heat exchange tube while increasing the contact area between the tube wall and the heat transfer medium, thereby improving and controlling the heat exchange efficiency.

4. Achieve cleaner production. The composite strip thread rolling adopts oil-free and chip-free processing, and has a very high internal surface cleanliness (uncleaned residue <0.30mg/m, only 30% after the rotary tube cleaning), which reduces environmental pollution.

5. Achieve high efficiency and high quality production. Both strip rolling speed and thread rolling speed can achieve high-speed production at speeds of up to 100-200 m/min, far exceeding the rate of drawing aluminum alloy internally threaded tubes (<60 m/min) by drawing method, and changing under normal conditions. The yield of composite strips for heat pipes is as high as 95% or more.

6. The composite strip is thinner and more reliable. The rolling thread method can be used to prepare heat exchange tubes of different thicknesses. Under the conditions of use, the wall thickness of the heat exchange tubes can be further reduced. At the same time, since the rolling method can accurately control the thickness of the strip, the thickness of the heat exchange tubes is uniform. , higher reliability.

7. The rolling thread method has lower processing cost. The rolling thread method enables high-speed production of large-size strips at a lower cost than the method of drawing internal threads.

DRAWINGS

1 is a manufacturing process flow of an aluminum alloy composite strip for an internally threaded heat exchange tube of the present invention;

2 is a schematic view showing the thread rolling of the aluminum alloy composite strip of the present invention;

3A is a schematic view showing the structure and layout of a stripless single-threaded thread of the present invention;

3B is a schematic view showing the structure and layout of the angled single-threaded thread of the strip of the present invention;

3C is a schematic view showing the structure and layout of the cross-threads of different angles of the strip according to the present invention;

4A is a schematic cross-sectional view showing an embodiment of an aluminum alloy composite strip according to the present invention;

4B is a schematic cross-sectional view showing an embodiment in which the side of the aluminum alloy composite strip has a rib.

Description of the reference numerals

1,6-mounting frame; 2-straight thread upper roll; 3,8-lower roll; 4-up roll width; 5-up roll thread surface width;

7-angled threaded roll; 9-angular thread width on the angled thread; 10-composite aluminum strip blank;

11-straight threaded composite aluminum strip; 12-cross threaded composite aluminum strip;

D1-thread upper tooth width; D2-thread tooth height; D3-thread lower tooth width; D4-slot bottom width; α-thread cusp angle;

D6-edge rib width; H-edge rib height; A-core material; B-leather material.

detailed description

The invention is further described below in conjunction with the drawings and embodiments.

The aluminum alloy composite strip for the internal thread heat exchange tube provided by the invention comprises a composite outer layer aluminum alloy and an inner layer aluminum alloy. The outer layer of aluminum alloy is also called brazing material, and is used for brazing connection with aluminum alloy fins on the prepared heat exchange tube; the inner layer of aluminum alloy is rolled with threads to increase the contact area between the tube wall and the heat transfer medium. At the same time, the heat transfer medium flows in the tube in a turbulent state. The invention provides the heat exchange tube prepared by the threaded aluminum alloy composite strip to replace the copper heat exchange tube, which can solve the problem that the heat exchange efficiency is low due to the connection between the heat transfer tube and the mechanical expansion tube of the aluminum alloy fin in the existing heat exchange system. The problem.

The "leather material" according to the present invention is also referred to as an outer layer aluminum alloy, or a solder layer, a skin layer, a skin material layer; the inner layer aluminum alloy includes a core material layer, and may also include other layer materials. In the present invention, the inner layer aluminum alloy refers to an aluminum alloy layer located inside the skin layer after the strip is welded into the heat exchange tube. Due to the embossing of the inner layer of the aluminum alloy, in the composite sheet having only the skin layer and the core layer, the inner layer of the aluminum alloy surface is also referred to as the embossed side. The outer aluminum alloy is compounded with the inner layer aluminum alloy, and is processed into an internally threaded heat exchange tube. The skin layer is used for welding with the heat dissipating fins or other parts, and the inner layer of the aluminum alloy is contacted with the heat transfer medium for heat exchange.

The present invention provides a method for producing the above-described aluminum alloy composite strip, which is obtained by rolling a thread on a composite strip to obtain an internal thread of a heat exchanger tube of a heat exchanger. The thread rolling method on the non-brazing side of the composite material can be used to make the internal thread with adjustable direction and structure. The production process is clean and efficient, combined with the subsequent high-speed high-frequency welding process, greatly improving the quality and production of the heat exchange tube product. Efficiency, compared with the existing method of cold drawing heat exchange tubes, the production is cleaner, the production efficiency is higher, the product quality is more stable, the wall thickness can be further reduced, and the processing cost is lower.

Taking a preferred embodiment as an example, as shown in Fig. 1, an aluminum alloy composite strip for an internally threaded heat exchange tube of the present invention and a method for producing the same will be described. The aluminum alloy composite strip is composed of a leather material 4 series aluminum alloy and a core material 3003 or a modified aluminum alloy thereof. The two alloys are melt-cast, composite, hot-rolled, cold-rolled, annealed, thread-rolled, and slit-cut. An aluminum alloy composite strip for internal thread heat exchange tubes. The strip is formed by tube forming, high-frequency welding into a tube, and brazed to the fin to form a heat exchanger, which can greatly improve heat exchange efficiency and production efficiency. The embossing is a kind of plastic deformation without volume loss, so metal chips are not generated during the rolling process, and high-speed production can be realized; and the ribbing method is a cutting preparation method, and the unnecessary portion is cut off, in order to Control surface quality and accuracy at a slower rate. The invention uses the composite strip material to replace the existing single strip material, so that the heat exchanger tube material achieves the two purposes of having both outer welding and inner rolling.

To achieve the above objective, the preferred embodiment specifically adopts the following technical solutions:

The invention provides a method for manufacturing an aluminum alloy composite strip for an internally threaded heat exchange tube, which is manufactured according to the following steps:

Smelting and casting into ingots. Each of the aluminum alloy raw materials in an appropriate ratio is separately subjected to smelting and casting to obtain each raw material blank ingot. In the present embodiment, a 4-series aluminum alloy and a 3-series aluminum alloy were taken and separately cast and obtained into a blank ingot of a 4-series aluminum alloy and a 3-series aluminum alloy.

The invention can manufacture aluminum alloy composite strips for internal thread heat exchange tubes of two layers, three layers or even multiple layers. In the step of smelting and casting into ingots, the raw materials of the aluminum alloys are selected according to requirements.

In the present invention, the material of the skin material and the core material is not particularly limited, as long as the skin material and the core material can be well compounded, the skin material can be welded, and the core material can be embossed to achieve the object of the present invention, but the inventor It is found that when the weight percentage of each element in the leather material is: Si is 7.0%-12.5%, Zn is 0-1.0%, the rest is Al and the content is less than 0.5% inevitable impurity element; the weight percentage of each element in the core material It is: Mn is 1.0%-1.8%, Cu is 0.1-0.8%, Ti is 0.1-0.25%, Zr is 0-0.2%, Fe is 0.1-0.3%, and the rest is Al and the content is less than 0.15%. The elements, the resulting heat exchange tubes take into account the welding performance, heat exchange performance and economy, the most reasonable design.

Of course, the scope of protection of the present invention is not limited to the materials selected for the leather material and the core material listed, and the material composition exemplified, as long as the material having good bonding force between the leather material and the core material can be used. The method of the present invention produces an internally threaded heat exchange tube which achieves different mechanical properties of the core material and the skin material, all of which fall within the scope of the present invention.

Next, the raw material blank ingot is subjected to surface treatment to remove impurities such as casting defects and scales on the surface of the ingot, thereby obtaining a surface-clean ingot.

After the surface treatment of the ingot is cleaned, hot rolling and cold rolling are performed until the specified thickness, for example, the thickness of the finished product in the cold rolling process is 0.2-1 mm.

In the hot rolling step, the clean core ingot and the hot rolled to a certain thickness of the skin material are combined in order and proportion, After hot rolling, a hot rolled composite strip is obtained. When the ingots of the clean core materials are taken by hot rolling, the outer aluminum alloy material generally takes 5%-15% of the total volume, so that the thickness of the final composite strip and the outer aluminum alloy accounts for the total thickness of the strip. 5%-15%. If the thickness of the outer aluminum alloy is less than 5%, the brazing layer is too thin, which affects the brazing quality of the heat exchange tube; if the thickness of the outer aluminum alloy is greater than 15%, the inner aluminum alloy is too thin, and the heat exchange tube is used. The life cannot be guaranteed and it is not conducive to the overall cost control of the heat exchange tube.

In the cold rolling step, if necessary, multiple cold rolling may be performed until the specified thickness.

annealing. The cold-rolled composite strip is annealed at a temperature of 330-420 ° C for 2-6 h, ensuring that the strip is completely recrystallized and softened, and a fully softened composite aluminum strip is obtained to facilitate subsequent thread rolling.

Next, the desired thread shape is rolled on the core surface of the softened composite aluminum strip blank (welded to the inner surface of the tube).

The process of thread rolling can be as shown in Fig. 2. The embossing machine used in the embossing step of this embodiment includes two sets of pressure rollers. A first set of pressure rollers is mounted on the mounting frame 1, and a second set of pressure rollers is mounted on the mounting frame 6. In the first group of press rolls, the lower roll 3 is a light roll, and the upper press roll 2 is a straight thread upper roll, and the core surface of the annealed composite aluminum strip blank 10 is directed upward, through the first set of press rolls, A straight threaded composite aluminum strip 11 is obtained, the specific thread being as shown in Figure 3A. In the second group of press rolls, the lower roll 8 is a light roll, the upper press roll 7 is an angled threaded upper roll, and the composite aluminum strip continues to pass through the second set of press rolls to obtain a cross-threaded composite aluminum strip 12, the details of the thread As shown in Figure 3C.

Of course, the thread of the present invention can also be individually rolled by a second set of press rolls to provide a thread with a rotational angle as shown in Figure 3B.

It should be understood by those skilled in the art that the term "thread" and "thread shape" as used in the present invention refers to a "thread" in a heat exchange tube, which is a surface shape such as a "thread" formed by the arrangement of the ribs and the grooves. , or "thread shapes" arranged in different directions intersect to form a surface shape as shown in FIG. 3C. The "thread shape" is set in order to change the flow state of the heat transfer medium in the heat exchange tube, increase the heat exchange contact area, thereby improving the heat exchange efficiency, so as long as the existing surface shape of the target can be achieved, such as the gap between the protrusion and the recess The surface shape and the like of the staggered arrangement are to be understood as "thread" or "thread shape" of the present invention.

The invention can control the thread pattern on the composite aluminum strip blank by selecting a suitable thread shape and a thread-oriented pressing roller according to the needs of the heat exchanger, thereby controlling the fluid turbulence in the heat exchange tube and achieving a good heat exchange effect. purpose. The inventors have found that when the tooth height D2 is 0.2-0.5 mm, the tooth bottom width is D3 (also called the thread lower tooth width) 0.2-0.8 mm, the groove bottom width D4 is 0.2-1.0 mm, and the apex angle α is 30- 60°, the thread rotation angle is 0-45°, and the number of threads is 40-80, the heat exchange tube produced has better heat exchange effect.

In the present invention, the operator rolls the required thread by adjusting the gap and parallelism of the entire roll. Because the gap of the roll directly affects the thickness of the edge to be welded, which affects the subsequent welding quality and the stability of the production process, In the manufacturing process of aluminum-rolled rolling thread, this patent adopts the following technical measures: (1) The embossing die processed by on-line electrolytic grinding technology with a surface roughness R of 0.04-0.02 μm is processed, and the embossing is performed simultaneously. The pressure and position are precisely controlled to ensure that the thread profile of the rolling is clear, tidy and full. The parameters of the thread (tooth height, tooth bottom width, apex angle, pitch, thread angle, number of racks) meet the design requirements. The cross-sectional shape of the rolled strip composite strip is as shown in Fig. 4A; (2) The composite aluminum strip is forcibly guided when entering the embossing machine and embossing, and at the edges of the two long sides of the strip during embossing A rib having a tooth height slightly lower than the standard tooth height and parallel to the longitudinal direction of the belt is rolled as shown in Fig. 4(b). The width D6 of the rib is generally 1-3 mm. In this embodiment, the rib width D6 is 2 mm, and the rib height H is generally selected within a range slightly lower than the standard tooth height of the thread, preferably 0.1-0.2 mm. The arrangement of the ribs can ensure that the composite aluminum strip does not have wave deformation during embossing, and at the same time increase the amount of molten metal in the welding zone during high-frequency welding, thereby ensuring the welding quality and obtaining a good shape of the finished product; 3) There is no debris generated during the embossing of the composite aluminum strip. After the embossing, the emulsion is blown dry with compressed air to ensure the cleanness of the inner surface of the tube.

Finally, cut. The composite strip after embossing is slit, and the irregular edge portion is cut off to obtain a composite strip for manufacturing a heat exchange tube. The long edge of the cut composite strip is cut from the original rib to form an equal rib extending in the longitudinal direction of the strip.

The pipe diameter of the heat exchange tube prepared by the invention is related to the parameter design of the embossing:

It can be known from the formula circumference = 2π (D/2) that the diameter D of the finally obtained heat exchange tube is related to the width W of the narrow strip obtained by slitting; and W=(D3+D4)×N+2×D6 The width W of the narrow band is related to the number of threads N, the lower tooth width D3 of each thread, the groove bottom width D4, and the rib width D6. As in the first embodiment below, the lower tooth width is about 0.4 mm, the groove bottom width is about 0.5 mm, and the width of each thread is about 0.4 + 0.5 = 0.9 mm; the width of 42 threads is about 42 x 0.9. = 37.8 mm, plus the width of the two ribs, the narrow strip width of this embodiment is 39.8 mm, plus tolerance, about 40 mm. From the relationship between the circumference of the formula and the diameter, it can be known that the diameter D of the heat exchange tube which can be finally obtained is about 12 mm. Those skilled in the art should be able to reasonably select from the above-exemplified preferred ranges according to actual needs, and obtain the relevant parameters of the desired heat exchange tubes after conversion by the relationship between the parameters.

The above embodiment is a method for manufacturing an aluminum alloy composite strip including a skin layer and a core layer. In addition, the present invention is also applicable to the manufacture of three or more layers of aluminum alloy composite strip, except for the aluminum alloy except the layer. The composite layer is referred to as an inner layer aluminum alloy, and the core layer aluminum alloy is one of the inner layer aluminum alloys. In other words, if the inner layer aluminum alloy includes the above-mentioned core layer, it may also comprise a composite anti-corrosion on the non-brazing side of the core material aluminum alloy (ie, the layer contacting the heat exchange medium after the heat exchange tube is formed). A layer of aluminum alloy to enhance the corrosion resistance of the heat exchanger. The anti-corrosion layer accounts for 5-15% of the total thickness of the strip, the thickness of the anti-corrosion layer is less than 5%, and the anti-corrosion effect is not achieved; the thickness of the anti-corrosion layer is higher than 15%, which is not conducive to the cost control and the strength requirements of the pipe. The weight percentage of each element in the anti-corrosion layer aluminum alloy is: Zn is 0.8-1.3%, and Fe is 0.2-0.4%, The Si content is less than 0.3%, and the balance is Al and the content of impurities below 0.15% is unavoidable.

When the composite sheet to be manufactured comprises an anticorrosive layer laminated on the core layer side, the steps are the same as the above steps, and only in the hot rolling step, the clean core ingot is ingot and hot rolled to a certain thickness of the sheet material and corrosion protection. The layers of the sheets are combined in order and proportion, and then hot rolled to obtain composite sheets. The thread is pressed against the softened composite strip anti-corrosion layer (that is, welded to the water-contact side of the tube).

The invention uses the process of rolling a thread on a composite strip by using a roll to replace the internal thread heat exchange tube prepared by cold drawing in the prior art, and the rolling speed of the rolling thread is 100-200 m/min, which can be higher than the subsequent one. The speed of the frequency welding process is matched to greatly improve the production efficiency.

The invention also discloses an aluminum alloy composite strip prepared by the above manufacturing method, which may be a double-layer aluminum alloy composite strip including an outer layer skin material and an inner layer core material, or may include an outer layer skin material and The inner layer of the core material, the anticorrosive layer of the three-layer aluminum alloy composite strip, and even the inner layer of the aluminum alloy layer comprises three or more layers of different materials of the aluminum alloy composite strip. The obtained two or more layers of the aluminum alloy composite strip are used to produce a heat exchange tube with internal threads.

The invention uses the above method to manufacture a system for an aluminum alloy composite strip for internal thread heat exchange tubes, including a melting furnace, a casting machine, a milling machine, a hot rolling mill, a cold rolling mill, an annealing furnace, a embossing machine, and a slitting machine. The aluminum alloy raw materials are sequentially passed through the above-mentioned equipment, and the finally obtained aluminum alloy composite strip can be used to manufacture internal thread heat exchange tubes. The above devices can be general-purpose devices in the field.

The invention will now be described in detail by way of specific examples. It should be noted that the numerical ranges involved in the following specific embodiments, such as the alloy component content, the process parameters, the parameters of the threads, etc., are exemplary illustrations of the present invention, and are not exhaustive. It should be understood that those skilled in the art, based on the above description, have the ability to replace the values in the following specific embodiments with other optional values in the corresponding numerical ranges according to actual needs, and finally obtain the required heat exchange. tube.

Embodiment 1:

This embodiment proceeds as follows:

1) Alloy casting: The aluminum alloy is prepared and cast according to the composition of grades AA4343 and AA3003Mod, and the ingot size is 400×1120×5100 mm. According to the mass percentage, the Si content in the AA4343 alloy is about 7.5%, and the rest is Al and less than 0.5% of unavoidable impurities; the AA3003Mod alloy has a Mn content of 1.5%, a Cu content of 0.35%, Fe of 0.25%, and a Ti content of 0.15. %, the rest is Al and a small amount of unavoidable impurity elements.

2) Composite hot rolling and cold rolling: AA4343 aluminum alloy ingot is surface-treated, heated to 500 ° C, then hot rolled to a thickness of 42 ± 1 mm, divided into 5100 mm sections, and combined with the surface treated AA3003Mod ingot and bundled , heated to 480 ± 10 ° C and kept for 12h, hot rolled to a thickness of 5 ± 1mm, finishing temperature is greater than 300 ° C, air cooled to room temperature After several times of cold rolling to a thickness of 0.4 ± 0.01 mm. Among them, the AA4343 aluminum alloy layer accounts for about 10% of the total thickness of the strip.

3) Annealing: The composite cold rolled coil is heated in a 360 ° C annealing furnace and then incubated for 4 h after warming.

4) Thread rolling: the thread is rolled at a speed of 120 m/min, the thread height is 0.2±0.05 mm, the tooth bottom width is 0.4±0.02 mm, the groove bottom width is 0.5±0.02 mm, the tooth tip angle is 30°, and the thread rotation angle is 0°. The number of internal threads is 42.

5) Strip cutting: slitting into a narrow strip of 40±0.1mm, and each strip has a longitudinal parallel rib (width×height: 1mm×0.15mm) on both sides of the narrow strip, as shown in Figures 3A and 4B. That is, the finished product without angled threaded composite strip.

The parallel single-thread composite strip produced in this embodiment can be made into a heat exchange tube with a diameter of about 12 mm by a coiled tube, which greatly improves the production efficiency of the tube, replaces the original copper heat exchange tube, and transfers the original heat transfer. The mechanical expansion tube connection of the system is improved to a brazed connection with good heat exchange effect.

Embodiment 2:

This embodiment proceeds as follows:

1) Alloy casting: The aluminum alloy is prepared and cast according to the composition of grades AA4045Mod and AA3003Mod, and the ingot size is 450×1450×4800mm. Among them, AA4045 Mod alloy has Si content of about 10.5%, Zn content of about 1.0%, and the rest is Al and content of less than 0.5% unavoidable impurity elements; AA3003Mod alloy has Mn content of about 1.6% and Cu content of about 0.65%. The Fe content was 0.12%, the Ti content was 0.12%, the Zr content was 0.13%, and the balance was Al and an unavoidable impurity having a content of less than 0.15%.

2) Composite hot rolling and cold rolling: AA4045Mod aluminum alloy ingot is surface-treated, heated to 500 ° C, then hot rolled to a thickness of 26 ± 1 mm, divided into 4800 mm sections, and combined with the surface treated AA3003Mod ingot and bundled , heated to 480 ± 10 ° C and kept for 16h, hot rolled to a thickness of 8 ± 1mm, the final rolling temperature is greater than 300 ° C, after the air cooling to room temperature, after multiple passes cold rolling to a thickness of 0.8 ± 0.01mm. Among them, AA4045Mod aluminum alloy layer accounts for about 5% of the total thickness of the strip.

3) Annealing: The composite cold rolled coil is baked in a 330 ° C annealing furnace and kept at a temperature for 6 h.

4) Thread rolling: the thread is rolled at a speed of 160m/min, the thread height is 0.3±0.05mm, the tooth bottom width is 0.4±0.02mm, the groove bottom width is 0.4±0.02mm, the tooth tip angle is 45°, and the thread rotation angle is 30°. The number of internal threads is 51.

5) Strip cutting and tube forming: slitting into a narrow strip of 43±0.1mm, and each strip has a longitudinally equal rib (width×height: 1mm×0.12mm) on both sides of the narrow strip, as shown in Fig. 3B. As shown in Fig. 4B, the finished product has an angled threaded composite strip.

The single-threaded composite strip with the rotation angle of 30° produced in this embodiment can be made into a heat exchange tube with a diameter of about 14 mm through the welding of the coiled tube, which greatly improves the production efficiency of the tube and replaces the original copper heat exchange tube. , the original heat transfer system The mechanical expansion pipe connection is improved to a brazed connection with better heat exchange effect.

Embodiment 3:

This embodiment proceeds as follows:

1) Alloy casting: The aluminum alloy is prepared and cast according to the composition of grades AA4047 and AA3003Mod, and the ingot size is 400×1120×5100 mm. Among them, the content of Si in AA4047 alloy is about 12%, the rest is Al and the content of impurities is less than 0.5%. The content of Mn in AA3003Mod alloy is 1.4%, the content of Cu is 0.8%, the content of Ti is 0.15%, and the content of Fe is 0.22. %, the balance is Al and the content of impurities below 0.15% is unavoidable.

2) Composite hot rolling and cold rolling: AA4047 aluminum alloy ingot is surface-treated, heated to 500 ° C, hot rolled to a thickness of 52 ± 1 mm, divided into 5100 mm sections, and composited and bundled with the surface treated AA3003Mod ingot. Heated to 480 ± 10 ° C and held for 12 h, hot rolled to a thickness of 6 ± 1 mm, the final rolling temperature is greater than 300 ° C, after the air cooling to room temperature, after multiple passes cold rolling to a thickness of 0.6 ± 0.01 mm. Among them, AA4047 aluminum alloy layer accounts for 12% of the total thickness of the strip.

3) Annealing: The composite cold rolled coil is baked in a 400 ° C annealing furnace, and then kept warm for 2 h.

4) Thread rolling: the thread is rolled at a speed of 100 m/min, the thread height is 0.2±0.05 mm, the tooth bottom width is 0.6±0.02 mm, the tooth tip angle is 60°, and the groove bottom width is 0.4±0.02 mm, which is 0° and 35. ° Cross thread, the number of internal threads is 58.

5) Strip cutting: slitting into a narrow strip of 62±0.5mm, and each strip has a longitudinal parallel rib (width×height: 1mm×0.1mm) on both sides of the narrow strip, as shown in Figures 3C and 4B. That is to say the cross-threaded composite strip finished product.

The cross-threaded composite strip produced in this embodiment can be made into a heat exchange tube with a diameter of about 20 mm by a coiled tube, which greatly improves the production efficiency of the tube, and the cross-thread change of the two-layer aluminum alloy composite strip preparation. The heat pipe replaces the original copper heat exchange tube, and the mechanical expansion pipe connection mode of the original heat transfer system is improved to a brazed connection, which has an excellent heat exchange effect.

Embodiment 4:

This embodiment proceeds as follows:

1) Alloy casting: Aluminum alloy is prepared and cast according to the composition of grades AA4047, AA3003Mod and AA7072, and the ingot size is 400×1120×5100 mm. Among them, the content of Si in AA4047 alloy is about 12.5%, the rest is Al and the content of impurities is less than 0.5%. The content of Mn in AA3003Mod alloy is 1.0%, the content of Cu is 0.2%, the content of Ti is 0.1%, and the content of Zr is 0.2. %, Fe content is 0.1%, the rest is Al and the content is less than 0.15% unavoidable impurities; AA7072 alloy has Zn content of 1.1%, Fe content is 0.3%, the rest is Al and the content is less than 0.15%. Free of impurity elements.

2) Composite hot rolling and cold rolling: AA4047 aluminum alloy ingot is surface-treated, heated to 500 ° C, hot rolled to a thickness of 52 ± 1 mm, and divided into 5100 mm segments; AA7072 aluminum alloy ingot is surface treated and heated to 500 ° C , hot rolled to a thickness of 26 ± 1mm, divided into 5100mm section; AA4047, AA7072 alloy and surface treated AA3003Mod ingot, stacked and bundled from top to bottom in the order of AA4047, AA3003Mod, AA7072 alloy, heated to 480 ±10 ° C and kept for 12 h, hot rolled to a thickness of 6 ± 1 mm, the final rolling temperature is greater than 300 ° C, after the air cooling to room temperature, after multiple passes cold rolling to a thickness of 0.6 ± 0.01 mm. Among them, AA4047 aluminum alloy layer accounts for 12% of the total thickness of the strip; AA7072 aluminum alloy layer accounts for 5% of the total thickness of the strip.

3) Annealing: The composite cold rolled coil is anneal in a 420 ° C annealing furnace and then incubated for 4 h after warming.

4) Thread rolling: the thread is rolled at a speed of 100 m/min, the thread height is 0.5±0.05 mm, the bottom of the tooth is 0.8±0.02 mm, the apex angle is 30°, and the groove bottom is 1.0±0.02 mm, which is 0° and 45. ° Cross thread, the number of internal threads is 40.

5) Strip cutting: slitting into a narrow strip of 74±0.2mm, and each strip has a longitudinal parallel rib (width×height: 1mm×0.18mm) on both sides of the narrow strip, as shown in Figures 3C and 4B. That is to say the cross-threaded composite strip finished product.

The cross-threaded composite strip produced in this embodiment can be made into a heat exchange tube having a diameter of about 24 mm by a coiled tube, which greatly improves the production efficiency of the tube, and the cross-thread change of the two-layer aluminum alloy composite strip is prepared. The heat pipe replaces the original copper heat exchange tube, and the mechanical expansion pipe connection mode of the original heat transfer system is improved to a brazed connection, which has an excellent heat exchange effect.

Embodiment 5:

This embodiment proceeds as follows:

1) Alloy casting: The aluminum alloy is prepared and cast according to the composition of grades AA4343, AA3003Mod and AA 7072, and the ingot size is 400×1120×5100 mm. Among them, the A content of AA4343 alloy is about 7%, the rest is Al and the content of impurities is less than 0.5%. The Mn content of AA3003Mod alloy is 1.8%, the content of Cu is 0.1%, the content of Ti is 0.25%, and the content of Fe is 0.3. %, the rest is Al and the content is less than 0.15% unavoidable impurities; the AA7072 alloy has a Zn content of 1.1%, an Fe content of 0.3%, and the balance is Al and a content of less than 0.15% of unavoidable impurity elements.

2) Composite hot rolling and cold rolling: AA4343 aluminum alloy ingot is surface-treated, heated to 500 ° C, hot rolled to a thickness of 34 ± 1 mm, and divided into 5100 mm sections. AA7072 aluminum alloy ingot is surface-treated and heated to 500 ° C. , hot rolled to a thickness of 42 ± 1mm, divided into 5100mm section; AA4343, AA7072 alloy and surface treated AA3003Mod ingot, stacked and bundled from top to bottom in the order of AA4343, AA3003Mod, AA7072 alloy, heated to 480 ± 10 ° C and kept for 12h, hot rolled to a thickness of 6 ± 1mm, the final rolling temperature is greater than 300 ° C, after the air cooling to room temperature, after multiple passes cold rolling to a thickness of 0.6 ± 0.01mm. Among them, AA4047 aluminum alloy layer accounts for 8% of the total thickness of the strip; AA 7072 aluminum alloy layer accounts for 10% of the total thickness of the strip.

3) Annealing: The composite cold rolled coil is baked in a 400 ° C annealing furnace, and then kept warm for 2 h.

4) Thread rolling: the thread is rolled at a speed of 100 m/min, the thread height is 0.2±0.05 mm, the tooth bottom width is 0.2±0.02 mm, the tooth tip angle is 45°, and the groove bottom width is 0.2±0.02 mm, which is 25° cross thread. The number of internal threads is 65.

5) Strip cutting: slitting into a narrow strip of 28 ± 0.1 mm, each strip having a longitudinal parallel rib (width × height: 1 mm × 0.15 mm) on both sides of the narrow strip, as shown in Figures 3B and 4B, That is, the finished product has an angled threaded composite strip.

The cross-threaded composite strip produced in this embodiment can be made into a heat exchange tube with a diameter of about 9 mm by the second coil welding, which greatly improves the production efficiency of the tube, and the cross-thread change of the two-layer aluminum alloy composite strip preparation. The heat pipe replaces the original copper heat exchange tube, and the mechanical expansion pipe connection mode of the original heat transfer system is improved to a brazed connection, which has an excellent heat exchange effect.

Example 6:

This embodiment proceeds as follows:

1) Alloy casting: The aluminum alloy is prepared and cast according to the composition of grades AA4343Mod and AA3003Mod, and the ingot size is 400×1120×5100mm. Among them, AA4343Mod alloy has Si content of about 7.8%, Zn content of 1.0%, and the rest is Al and content of less than 0.5% unavoidable impurity elements; AA3003Mod alloy has Mn content of 1.7%, Cu content of 0.5%, and Ti content of 0.2. %, Zr content is 0.1%, Fe content is 0.15%, and the balance is Al and the content is less than 0.15%.

2) Composite hot rolling and cold rolling: AA4343Mod aluminum alloy ingot is surface-treated, heated to 500 ° C, hot rolled to a thickness of 34 ± 1 mm, divided into 5100 mm sections, and composited and bundled with the surface treated AA3003Mod ingot. Heated to 480 ± 10 ° C and held for 12 h, hot rolled to a thickness of 6 ± 1 mm, the final rolling temperature is greater than 300 ° C, after the air cooling to room temperature, after multiple passes cold rolling to a thickness of 0.6 ± 0.01 mm. Among them, AA4047 aluminum alloy layer accounts for 8% of the total thickness of the strip.

3) Annealing: The composite cold rolled coil was annealed in a 340 ° C annealing furnace for 6 h after warming.

4) Thread rolling: the thread is rolled at a speed of 100 m/min, the thread height is 0.4±0.05 mm, the tooth bottom width is 0.3±0.02 mm, the tooth tip angle is 60°, and the groove bottom width is 0.7±0.02 mm, which is 15° and 45. ° Cross thread, the number of internal threads is 80.

5) Strip cutting: slitting into a narrow strip of 82±0.2mm, and each strip has a longitudinal parallel rib (width×height: 1mm×0.2mm) on both sides of the narrow strip, as shown in Figures 3C and 4B. That is to say the cross-threaded composite strip finished product.

The cross-threaded composite strip produced in this embodiment can be made into a heat exchange tube with a diameter of about 26 mm by a coiled tube, which greatly improves the production efficiency of the tube, and the cross-thread change of the two-layer aluminum alloy composite strip is prepared. The heat pipe replaces the original copper heat exchange tube, and the mechanical expansion pipe connection mode of the original heat transfer system is improved to a brazed connection, which has an excellent heat exchange effect.

The aluminum alloy composite strip and the manufacturing method thereof provided by the present invention are described in detail above. The principles and embodiments of the present invention are described in the following. The description of the above embodiments is only used to help understanding. The method of the present invention and its core idea; at the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and the scope of application. It is understood to be a limitation of the invention.

Claims (10)

1. The invention relates to a method for manufacturing an aluminum alloy composite strip for an internal thread heat exchange tube, wherein the aluminum alloy composite strip is used for producing an internally threaded heat exchange tube, characterized in that the method comprises the following steps:

   Smelting and casting into ingots, smelting each of the aluminum alloy raw materials, and casting each of the blank ingots;

   Surface treatment, surface milling of each blank ingot to obtain clean ingots of various surfaces;

   Composite hot rolling, hot rolling of each surface clean ingot to obtain a hot rolled composite strip comprising an outer layer of aluminum alloy and an inner layer of aluminum alloy;

   Cold rolling, the hot rolled composite strip is cold rolled in multiple passes to obtain a cold rolled composite strip;

   Annealing, annealing the cold rolled composite strip to obtain a fully softened composite aluminum strip;

   Thread rolling, rolling a thread on the inner aluminum alloy surface of the softened composite aluminum strip to obtain a threaded composite strip;

   The slitting is performed, and the threaded composite strip is slit to obtain a composite strip for manufacturing a heat exchange tube.
2. The method according to claim 1, wherein the weight percentage of each element in the outer aluminum alloy is: 7.0% to 12.5% for Si, 0% to 1.0% for Zn, and the balance of Al and less. 0.5% inevitable impurity element;

   The weight percentage of each element in the inner layer aluminum alloy is: Mn is 1.0%-1.8%, Cu is 0.1-0.8%, Ti is 0.1-0.25%, Zr is 0-0.2%, and Fe is 0.1-0.3%. The balance is Al and an impurity element of less than 0.15% inevitably.
3. The manufacturing method according to claim 1, wherein said inner layer aluminum alloy comprises a core material layer aluminum alloy and an anticorrosive layer aluminum alloy, said core material layer aluminum alloy being located in said intermediate outer layer aluminum alloy and said The anti-corrosion layer is between the aluminum alloys; the anti-corrosion layer accounts for 5-15% of the total thickness of the strip.
4. The method according to claim 3, wherein the weight percentage of each element in the aluminum alloy of the anticorrosive layer is: Zn is 0.8-1.3%, Fe is 0.2-0.4%, Si content is less than 0.3%, and the rest It is an inevitable impurity element for Al and a content of less than 0.15%.
5. The manufacturing method according to claim 1, wherein the outer aluminum alloy has a thickness of 5% to 15% of the total thickness of the strip;

   The cold rolled composite strip obtained by the cold rolling step has a thickness of 0.2 to 1 mm.
6. The method according to claim 2, wherein the annealing step has an annealing temperature of 330 to 420 ° C and a holding time of 2 to 6 hours.
7. The manufacturing method according to claim 2, wherein in said thread rolling step, a rib parallel to the longitudinal direction of the strip is rolled at each of the edges of the long sides of the softened composite strip. The width of the rib is 1mm, high 0.1-0.2mm.
8. The manufacturing method according to claim 7, wherein in the thread rolling step, the thread obtained by the thread rolling step has a tooth height of 0.2-0.5 mm and a tooth bottom width of 0.2-0.8 mm. The groove bottom has a width of 0.2-1.0 mm, a tip angle of 30-60°, a thread rotation angle of 0-45°, and a thread number of 40-80.
9. The manufacturing method according to claim 7, wherein in the thread rolling step, two or more sets of embossing machines are used for embossing, and the threads on the obtained threaded plate are crossed threads.
10. An aluminum alloy composite strip for internally threaded heat exchange tubes, which is obtained by the production method according to any one of claims 1-9.

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