A process for producing aluminum alloy coiled bar suitable for cold heading production of parts

Abstract

The application relates to an aluminum alloy coil bar production process suitable for cold upsetting production of parts, which comprises the following steps: S1 fast cooling continuous casting of aluminum alloy disc round rod material; S2 differential temperature continuous expansion-compression extrusion; S3 online quenching cooling; S4 online surface roughening treatment; S5 online surface phosphating lubrication treatment; and S6 coiling; the step S2 solves the problem that the middle deformation is too small in the extrusion process of material change from small to large by controlling the expansion-compression section temperature T2 to be higher than the temperature T1 at the expansion inlet and the temperature T3 at the product outlet; meanwhile, the continuous expansion-compression extrusion cavity is arranged in a short expansion cone and long compression cone structure to increase the deformation degree of the continuous extrusion. The application realizes large plastic deformation by jointly using the continuous extrusion severe shearing deformation and the differential temperature expansion-compression deformation in the same process, and obtains the extruded coil material with uniform structure, refined grains and high solid solubility by combining with the online quenching cooling; after the coil material is used for cold upsetting production of parts, the coil material does not need solid solution treatment and can obtain higher hardness after manual aging.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of metal plastic working, and particularly relates to a production process of aluminum alloy coiled bar material suitable for cold upsetting parts. BACKGROUND

[0002] With the rapid development of automobile lightweight technology, a large number of automobile chassis parts manufactured by cold upsetting of steel coiled bar materials are gradually replaced by aluminum alloys, and the diameter of the aluminum alloy coiled bar material is generally in the range of 50-150mm. The medium-strength Al-Mg-Si series aluminum alloy coiled bar material has medium strength, good formability, weldability and corrosion resistance, and is widely used in lightweight parts such as automobile shock absorbers and chassis parts.

[0003] At present, the production process of aluminum alloy bar material mainly includes semi-continuous ingot casting-extrusion method and semi-continuous bar casting hot rolling method. The semi-continuous ingot casting-extrusion method includes the following processes: semi-continuous casting, ingot homogenization, ingot heating, hot extrusion and aluminum alloy bar material. Due to the limitation of the weight of the extruded ingot, the product is mainly a straight bar or a single-coil jointless small-weight coiled bar material (usually not more than 200Kg), and due to the friction between the extruded ingot and the extrusion cylinder, the extrusion force gradually decreases with the extrusion, and the extrusion temperature gradually increases due to the deformation heat and the friction, so the head-tail performance of the forward extrusion product is very uneven, and therefore the process cannot solve the technical problem of the uneven product organization and performance along the length of the conventional forward extrusion product. With the popularization of high-speed automatic manufacturing technology of automobile parts, these small-weight coiled bar materials have been difficult to meet the use requirements of high-speed automatic manufacturing technology.

[0004] In order to improve the length of the bar and wire material, in recent years, the semi-continuous bar casting hot rolling method has been developed and applied. The semi-continuous casting bar after heating is rolled in multiple stands, and the front and rear rolling mill pass is alternately pressed in the width and height directions of the rolled piece, so as to realize the deformation processing from large-section billet to small-section bar material. Compared with the fixed length of the semi-continuous ingot-extrusion method, the semi-continuous bar casting hot rolling method can use a semi-continuous ingot with a length of about 10m, and after hot rolling, a larger coiled bar material (currently up to 300Kg) can be obtained. However, the size precision of the hot rolled bar material is poor, which cannot meet the requirements of the cold upsetting manufacturing process, and it must also be subjected to drawing and annealing treatment. This not only increases the processing procedures and production cost, but also the strengthening phase will precipitate and coarsen after annealing, so the cold upsetting parts using this material must be subjected to solid solution quenching treatment to improve the strength or hardness, but this process may also produce coarse grain structure, thereby affecting the performance and uniformity of the parts. SUMMARY

[0005] (I) Technical problems to be solved

[0006] In view of the above-mentioned shortcomings and deficiencies of the prior art, the present application provides an aluminum alloy coil bar production process suitable for cold heading production of parts, which mainly processes fast-cooling continuous casting aluminum alloy disc round rod material through differential temperature continuous expansion-compression extrusion, which realizes large plastic deformation by jointly using continuous extrusion severe shear deformation and differential temperature expansion-compression deformation in the same process, and further combines online quenching cooling process to obtain extruded coil material (primary product) with uniform structure, grain refinement and high solid solubility, thereby solving the problems that the current semi-continuous ingot-extrusion method is difficult to produce large coil weight coil bar material and the product structure and performance are very uneven along the length, and the semi-continuous casting rod hot rolling method requires solid solution quenching treatment for the product cold heading parts, thereby causing the technical problem of coarse grains. The present application provides a solution for the production of large coil weight aluminum alloy coil bar raw material required for high-speed automatic cold heading production of automobile parts.

[0007] (II) Technical solutions

[0008] In order to achieve the above-mentioned purpose, the main technical solutions adopted by the present application include:

[0009] In a first aspect, the present application provides an aluminum alloy coil bar production process suitable for cold heading production of parts, comprising the following steps: S1, fast-cooling continuous casting of aluminum alloy disc round rod material; S2, differential temperature continuous expansion-compression extrusion; S3, online quenching cooling; S4, online surface roughening treatment; S5, online surface phosphating lubrication treatment; and S6, coiling.

[0010] In S2, the differential temperature continuous expansion-compression extrusion is realized by using a continuous expansion-compression extrusion cavity, which comprises, in order, an expansion inlet, a first gradually expanding section, a second gradually contracting section, a third gradually contracting section, a sizing belt, and a cavity outlet according to the alloy flow sequence; the expansion inlet is connected to a feeding plate, the cavity inner diameter of the first gradually expanding section is gradually expanded from the expansion inlet so that the first gradually expanding section is conical, the cavity inner diameter of the second gradually contracting section is gradually contracted so that the second gradually expanding section is inverted conical, the cavity inner diameter of the third gradually contracting section is gradually contracted so that the third gradually expanding section is inverted conical, and the contraction speed of the third gradually contracting section is smaller than that of the second gradually contracting section, and the length of the third gradually contracting section is more than 3 times the length of the second gradually contracting section; wherein the first gradually expanding section, the second gradually contracting section, and the third gradually contracting section constitute the expansion-compression extrusion section of the cavity.

[0011] Wherein, the ratio L / D of the length L of the third gradually contracting section to the cavity inner diameter D of the sizing belt is controlled to be 1-3, so that the continuous expansion-compression extrusion cavity is of short expansion cone and long compression cone structure.

[0012] And the S2 step further comprises: controlling the temperature T2 at the junction of the first gradually expanding section and the second gradually contracting section to be higher than the temperature T1 at the expansion inlet and the outlet temperature T3 of the sizing belt.

[0013] In this invention, controlling the L / D ratio between 1 and 3 is primarily beneficial for achieving severe shear deformation during extrusion of the billet, thereby increasing the degree of deformation during continuous extrusion. Online water quenching and cooling mainly involves water quenching and cooling the product exiting the die cavity, while simultaneously spraying water to cool the die cavity exit end face.

[0014] The inner diameter of the sizing die cavity directly determines the diameter of the continuously expanding-compressing extruded product. Therefore, the inner diameter D of the sizing die cavity is equal to the product diameter. At the same time, compared with the "semi-continuous hot rolling method of casting rods", the aluminum alloy coil rods produced by this invention have higher dimensional accuracy.

[0015] Preferably, a heating element is provided at the junction of the first expanding section and the second contracting section to achieve the goal that the temperature T2 at the junction of the first expanding section and the second contracting section is higher than the temperature T1 at the expansion inlet and the outlet temperature T3 of the sizing belt. This ensures that the temperature of the expansion-compression extrusion section is higher than the temperature at the expansion inlet and the outlet temperature of the sizing belt. This treatment is beneficial to the expansion radial deformation, so as to solve the problem that the deformation in the middle is usually too small during the extrusion process of the material from small to large.

[0016] Preferably, T2 = 480-540℃, T1 = 320-400℃, and T3 = 280-340℃. These temperature ranges are mainly determined based on the type of aluminum alloy (chemical composition). Temperature T2 is used to address the issue of smaller deformation in the middle of the material during extrusion, while T1 and T3 are also intended to meet the requirement of uniform deformation at the corresponding stages.

[0017] Preferably, the heating element is an electric heating wire or an induction heating element.

[0018] Preferably, the length L of the third tapering section is (1~3)×D. Preferably, the length of the first expanding section is 20mm and the length of the second tapering section is 10mm. Preferably, the expansion angle of the first expanding section is 100°-135° (cone angle). Preferably, the contraction angle of the second tapering section is 60-90° (cone angle). Preferably, the contraction angle of the third tapering section is 10-15° (cone angle). Preferably, the mold cavity outlet is an outwardly flared trumpet shape. The above are some reference parameters for manufacturing the continuously expanding-compression extrusion mold cavity, but they should not be used as limiting conditions for implementing the present invention.

[0019] Preferably, S3 includes: directly applying water quenching cooling treatment to the product extruded by differential temperature continuous expansion-compression and the mold cavity outlet, rapidly cooling and quenching the product, while controlling the temperature T3 to maintain it at a low temperature.

[0020] The most significant improvement and innovation of this invention lies in the fact that, through the processing step S2, two methods—continuous extrusion and intense shear deformation, and differential temperature expansion-compression deformation—are combined in the same process to achieve large plastic deformation. Furthermore, based on S2, the online quenching and cooling in step S3 is incorporated to obtain an extruded coil with uniform microstructure, refined grains, and high solid solubility. This extruded coil is the initial product. Steps S3-S6 and step S1 can be performed according to conventional methods; however, in this invention, they are more preferably operated as follows.

[0021] Preferably, the rapid cooling continuous casting in step S1 yields an aluminum alloy disc-shaped billet with a diameter of 20mm ± 0.5mm, which is then subjected to differential temperature continuous expansion-compression extrusion in step S2 to produce a round bar coil with a diameter of 25-45mm. In step S1, preferably, the cooling rate of the rapid cooling continuous casting is 200-350℃ / s.

[0022] Preferably, step S4 includes: performing an online roughening treatment on the surface of the product obtained by online quenching and cooling; preferably, the roughening treatment is performed using a steel brush. After the surface roughening treatment, the aluminum alloy product has a lower surface roughness and a more uniform and delicate surface texture. From a microscopic morphology perspective, the product surface has many evenly distributed small pits.

[0023] Preferably, step S5 includes: performing an online surface phosphating lubrication treatment on the roughened product. The online roughening treatment in S4 and the online surface phosphating lubrication treatment in S5 are mainly to obtain a uniform and good lubrication layer, which is beneficial for subsequent cold heading forming of parts.

[0024] The online surface phosphating lubrication treatment includes, but is not limited to, phosphating-saponification treatment. The phosphating-saponification process involves heating the phosphated polymeric lubricant to a temperature maintained at 50-70°C for 30-120 seconds, followed by drying; more preferably, the temperature is maintained at 60-65°C for 60-90 seconds. Phosphating lubrication treatment provides protection for aluminum alloy products, preventing metal corrosion; it also acts as a friction reducer and lubricant in cold working processes.

[0025] Preferably, step S6 includes: using a three-point bending wheel to roll the material clockwise or counterclockwise according to a preset weight or length.

[0026] Secondly, the present invention provides an aluminum alloy coil product suitable for cold heading of parts, which is prepared by the production process of any of the above embodiments.

[0027] Thirdly, the present invention also relates to an aluminum alloy coil raw material for cold heading of automobile chassis parts, which is prepared by the production process of any of the above embodiments.

[0028] The aluminum alloy coils provided by this invention, when used for cold heading of automotive chassis parts, eliminate the need for solution treatment after cold heading, allowing for direct artificial aging. This saves subsequent manufacturing processes and improves the mechanical properties of the parts. In particular, this invention provides high-quality, large-coil aluminum alloy raw materials for high-speed automated cold heading of automotive parts.

[0029] The aluminum alloy coils and bars provided by this invention can be used to manufacture various small forgings, and are especially suitable for producing automotive chassis parts.

[0030] (III) Beneficial Effects

[0031] (1) The production process of this invention involves differential temperature continuous expansion-compression extrusion processing of rapidly cooled continuous cast aluminum alloy coils and rods. This processing method combines continuous extrusion with intense shear deformation and differential temperature expansion-compression deformation to achieve large plastic deformation. Combined with online quenching and cooling, it yields extruded coils with uniform microstructure, refined grains, and high solid solubility. The aluminum alloy coils and rods produced by this invention are not limited by the process and can produce aluminum alloy coils and rods of various specifications, including small coils, medium and large coils (≥300Kg), or extra-large coils (≥500Kg). This provides high-quality, large-coil aluminum alloy coil and rod raw materials for high-speed automated cold heading production of automotive parts.

[0032] (2) After the aluminum alloy coils and bars of the present invention are cold-forged into parts, there is no need to perform solid solution treatment on the parts and they can be directly artificially aged, which saves process costs for subsequent processing and enables subsequent parts to have better mechanical properties.

[0033] (3) This invention proposes a new process for producing aluminum alloy coils and bars. Unlike existing technologies, the product dimensions are directly determined by the inner diameter of the sizing zone of the continuous expansion-compression extrusion die. Compared to the "semi-continuous casting hot rolling method," the aluminum alloy coils and bars produced by this invention have higher dimensional accuracy, solving the technical problems of poor dimensional accuracy in the semi-continuous casting hot rolling method. Compared to the current semi-continuous casting-extrusion method, the production process of this invention produces aluminum alloy coils and bars whose length or weight is not limited by the process, solving the technical problem that existing processes are difficult to produce large and heavy coils. In addition, the extrusion temperature and extrusion pressure in the production process of this invention are independent of the length or volume of the extruded material, thus overcoming the problem of uneven product structure and properties along the length in existing technologies.

[0034] (4) By setting heating elements, the temperature of the expansion-compression extrusion section of the continuous expansion-compression extrusion die cavity is controlled to be higher than the temperature at the expansion inlet and the temperature at the sizing belt outlet, which is beneficial to the expansion radial deformation and solves the problem of the size of the deformation in the middle during the extrusion process of the material from small to large. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of a continuously expanding-compression extrusion cavity, which is a preferred embodiment of the production process of the present invention. Detailed Implementation

[0036] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] like Figure 1 The diagram shows a schematic of a continuous expansion-compression extrusion die cavity used in a preferred embodiment of the production process of this invention. The continuous expansion-compression extrusion die cavity includes, in sequence, an expansion inlet 1, a first expanding section 2, a second contracting section 3, a third contracting section 4, a sizing band 5, and a die cavity outlet 6, arranged according to the alloy flow sequence. The expansion inlet 1 connects the inside and outside of the die cavity for feeding aluminum alloy disc / rod material. The inner diameter of the first expanding section 2 gradually expands from the expansion inlet 1, making the first expanding section 2 conical. The inner diameter of the second contracting section 3 gradually contracts, making the second expanding section 3 inverted conical. The inner diameter of the third contracting section 4 gradually contracts, making the third expanding section 4 inverted conical. The contraction speed of the third contracting section 4 is less than that of the second contracting section 3, and the length of the third contracting section 4 is much greater than (more than 3 times) the length of the second contracting section 3. The first expanding section, the second contracting section, and the third contracting section constitute the expansion-compression extrusion section of the die cavity. The sizing belt 5 is used to determine the size of the product, and the mold cavity outlet 6 is used to discharge the product. The mold cavity outlet 6 is preferably designed as a flared horn. A heating element 31 is provided at the junction of the first expanding section 2 and the second contracting section 3. The heating element 31 is either an electric heating wire or an induction heating element.

[0038] like Figure 1 As shown, to facilitate the installation of the heating element, the continuous expansion-compression extrusion cavity can be configured as a combined structure. The expansion inlet 1 and the first expanding section 2 are located on the first mold assembly, while the second contracting section 3, the third contracting section 4, the sizing band 5, and the cavity outlet 6 are located on the second mold assembly. The first and second mold assemblies are combined to obtain the continuous expansion-compression extrusion cavity, and the heating element 31 is located at the junction of the two molds. The length L of the third contracting section 4 is 1-3 times the inner diameter D of the cavity of the sizing band 5, making the continuous expansion-compression extrusion cavity a short expansion cone and a long compression cone structure to increase the deformation degree of continuous extrusion.

[0039] In the continuous expansion-compression extrusion die cavity, the expansion inlet 1 is the feed inlet of the rod material, the first gradually expanding section 2 is for expansion, the second gradually contracting section 3 is the transition section for expansion to compression extrusion (forming the expansion section of the die cavity with the first gradually expanding section 2, and forming the compression extrusion section of the die cavity with the third gradually contracting section 4), the third gradually contracting section 4 is the main compression extrusion section (the third gradually contracting section is also called the compression cone), the sizing zone 5 is the section that determines the size of the output product, and the die cavity outlet 6 provides the outlet for the product.

[0040] exist Figure 1 In the specific structure shown, the inner diameter D of the mold cavity of the sizing belt 5 is 25-45mm (product diameter), the length L of the third tapering section 4 is (1~3)×D, the diameter of the expansion inlet 1 is 20mm, the length of the first expanding section is 20mm, the length of the second tapering section is 10mm, the expansion angle of the first expanding section 2 is 100°, the contraction angle of the second tapering section 3 is 120°, and the contraction angle of the third tapering section is 20°. The length of the sizing belt 5 is 5mm. The above describes the manufacturing process. Figure 1 The parameters of the continuously expanding-compression extrusion cavity of the specific structure shown are not intended to limit the implementation of the present invention.

[0041] In the production of aluminum alloy coils for cold heading components, the temperature T2 at the junction of the first expanding section and the second contracting section must be controlled to be higher than the temperature T1 at the expansion inlet and the outlet temperature T3 of the sizing zone. Preferably, T2 = 480-540℃, T1 = 320-400℃, and T3 = 280-340℃.

[0042] The following description is based on preferred embodiments of the present invention.

[0043] Example 1

[0044] This embodiment provides a production process for aluminum alloy coils suitable for cold-heading automotive chassis parts. The product is 6061 aluminum alloy with a target diameter of 27.2 mm and a coil weight of not less than 300 kg, replacing the steel coils currently used for cold-heading automotive chassis parts. The production process for this aluminum alloy coil is as follows:

[0045] (1) Rapid cooling continuous casting: 99.7% aluminum ingots, rapidly soluble Si, magnesium ingots, and Al-5Cr and Al-10Cu master alloys were used. The weight ratio of each alloy was calculated based on the chemical composition range of 6061 aluminum alloy. The materials were prepared according to this ratio and then melted, refined, held, and filtered online in a dual 1000Kg capacity gas-fired melting furnace. Samples were then taken for alloy chemical composition analysis, as shown in Table 1. Horizontal continuous casting was used to continuously cast rods with a diameter of 20mm. The continuous casting temperature was controlled at 710-720℃, and the casting speed was set at 1000mm / min. The cooling rate was controlled to be approximately 340℃ / s by controlling the length of the cooling section and the water volume.

[0046] (2) Differential temperature continuous expansion-compression extrusion: On a 400-type aluminum continuous extrusion press, a differential temperature continuous expansion-compression die cavity (the length of the third shrinkage section L = 60 mm, and the length of the second shrinkage section 10 mm) is used to extrude coiled bars with a diameter of 27.2 mm (the inner diameter of the die cavity is precisely measured by setting the sizing belt). The extrusion wheel speed is 8 rpm, the temperature of the wheel groove is controlled at about 350℃ (considered as T1), the temperature of the die cavity outlet is about 295℃ (considered as T3), and the temperature of the die cavity expansion-compression section T2 is controlled at about 530℃ using heating and heat preservation elements.

[0047] (3) Online water quenching: Cooling water is sprayed onto the end face of the mold cavity to quickly cool and quench the product, while the temperature T3 is controlled to maintain a low temperature.

[0048] (4) Online texturing treatment: The surface of the quenched and cooled bar is texturized online by a pair of high-speed rotating steel brushes.

[0049] (5) Online surface phosphating lubrication treatment: The rod material in the roughening process is subjected to phosphating-saponification treatment by using commercially available aluminum alloy cold extrusion lubricant and mold release agent F701 in the phosphating lubrication treatment tank after the steel brush machine: The temperature of the phosphating polymer lubricant is maintained at 65℃ by circulating heating, and the length of the treatment tank is adjusted to ensure that the treatment time is 60s before drying.

[0050] (6) Rolling: A three-point bending wheel winding machine is used to roll the product counterclockwise according to the user's requirements, with a weight of about 350Kg.

[0051] Finally, samples were taken from the head and tail of the 6061 aluminum alloy coil and bar, as well as from the customer's cold-forged automotive chassis parts, and subjected to aging treatment at 175℃ for 8 hours. The measured mechanical properties of the 6061 aluminum alloy coil and bar and the hardness values ​​of the cold-forged parts are shown in Table 2.

[0052] Example 2

[0053] This embodiment provides a production process for aluminum alloy coils suitable for cold-heading automotive chassis parts. The product is 6082 aluminum alloy with a target diameter of 42.8 mm and a coil weight of not less than 500 kg, replacing the steel coils currently used for cold-heading automotive chassis parts. The production process for this aluminum alloy coil is as follows:

[0054] (1) Rapid cooling continuous casting: 99.7% aluminum ingots, rapidly soluble Si, magnesium ingots, and Al-5Mn and Al-5Cr master alloys were used. The weight ratio of each alloy was calculated based on the chemical composition range of 6082 aluminum alloy. The materials were prepared according to this ratio and then melted, refined, held, and filtered online in a dual 1000Kg capacity gas-fired melting furnace. Samples were then taken for alloy chemical composition analysis, as shown in Table 1. Horizontal continuous casting was used to continuously cast rods with a diameter of 20mm. The continuous casting temperature was controlled at 720-730℃, and the casting speed was set at 900mm / min. The cooling rate was controlled to approximately 320℃ / s by controlling the length of the cooling section and the water volume.

[0055] (2) Differential temperature continuous expansion-compression extrusion: On a 400-type aluminum continuous extrusion press, a differential temperature continuous expansion-compression die cavity (the length of the third shrinkage section L = 100 mm, and the length of the second shrinkage section 15 mm) is used to extrude coiled bars with a diameter of 42.8 mm. The extrusion wheel speed is 10 rpm, the temperature of the wheel groove is controlled at about 340℃ (considered as T1), the die exit temperature is about 300℃ (considered as T3), and the temperature T2 of the die cavity expansion-compression section is controlled at about 520℃ using heating and heat preservation elements.

[0056] (3) Online water quenching: Cooling water is sprayed onto the mold cavity outlet end face to quickly cool and quench the product, while the temperature T3 is controlled to maintain a low temperature.

[0057] (4) Online texturing treatment: The surface of the quenched and cooled bar is texturized online by a pair of high-speed rotating steel brushes.

[0058] (5) Online surface phosphating and lubrication treatment: The rod material in the roughening process is subjected to phosphating-saponification treatment by using commercially available aluminum alloy cold extrusion lubricant and mold release agent F701 in the phosphating and lubrication treatment tank after the steel brush machine: The phosphating polymer lubricant is heated in a circulating manner and the temperature is maintained at 70℃. The length of the treatment tank is adjusted to ensure that the treatment time is 90s and then dried.

[0059] (6) Rolling: A three-point bending wheel winding machine is used to roll the product counterclockwise according to the user's requirements, with a weight of about 500Kg.

[0060] Finally, samples were taken from the head and tail of the 6082 aluminum alloy coil and bar, as well as from the customer's cold-forged automotive chassis parts, and subjected to aging treatment at 175℃ for 5 hours. The measured mechanical properties of the 6082 aluminum alloy coil and bar and the hardness values ​​of the cold-forged parts are shown in Table 2.

[0061] Table 1. Main chemical composition (weight percentage, %) of the 6061 and 6082 aluminum alloys of this invention

[0062] Alloy Si Fe Cu Mn Mg Cr Zn Ti 6061 0.617 0.113 0.304 0.012 0.901 0.235 0.027 0.012 6082 0.942 0.102 0.056 0.561 0.839 0.014 0.012 0.009

[0063] Table 2 Performance test results of 6061 and 6082 aluminum alloy coils and cold-headed parts of this invention

[0064]

[0065] As shown in Table 2, the 6061 and 6082 aluminum alloy coils produced using the manufacturing process of this invention, after being cold-forged into automotive chassis parts by customers, underwent standard aging treatment on the head and tail of the aluminum alloy coils and the cold-forged parts. The performance test results of the head and tail of the coils were consistent (indicating that the microstructure and properties of the coils were relatively uniform along the length). The mechanical properties of the coils and cold-forged parts were excellent, far exceeding the technical specifications required by automotive chassis parts manufacturers. The products exhibited good lubrication during the cold-forging process, ensuring dimensional accuracy and surface quality (0.8-1.6μm) of the parts, with a yield rate as high as 90%. In summary, this invention proposes a new process for producing aluminum alloy coils and bars. Compared to the "semi-continuous casting hot rolling method," the aluminum alloy coils and bars produced by this invention have higher dimensional accuracy. Compared to the "semi-continuous casting-extrusion method," this invention can produce aluminum alloy bars of arbitrary length and weight, and overcomes the problem of highly uneven microstructure and properties along the length of the product. More importantly, the aluminum alloy bar raw materials prepared by this invention, after being cold-headed into parts, do not require solution quenching treatment and can be directly artificially aged. The mechanical properties of the parts, especially their strength or hardness, are significantly higher than the user's purchasing specifications and the product standards for the parts.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for producing aluminum alloy coils and bars suitable for cold heading of parts, characterized in that, The process includes the following steps: S1, rapid cooling continuous casting of aluminum alloy disc and rod stock; S2, differential temperature continuous expansion-compression extrusion; S3, online quenching and cooling; S4, online surface roughening treatment; S5, online surface phosphating and lubrication treatment; S6, coiling. In S2, the differential temperature continuous expansion-compression extrusion is achieved using a continuous expansion-compression extrusion die cavity. This die cavity, following the alloy flow sequence, includes a sequentially connected expansion inlet, a first gradually expanding section, a second gradually contracting section, a third gradually contracting section, a sizing zone, and a die cavity outlet. The expansion inlet connects to the feed plate. The inner diameter of the first gradually expanding section gradually expands from the expansion inlet, making the first gradually expanding section conical. The inner diameter of the second gradually contracting section gradually contracts, making the second gradually expanding section inverted conical. The inner diameter of the third gradually contracting section gradually contracts, making the third gradually expanding section inverted conical. Furthermore, the contraction speed of the third gradually contracting section is less than that of the second gradually contracting section, and the length of the third gradually contracting section is more than three times the length of the second gradually contracting section. The first gradually expanding section, the second gradually contracting section, and the third gradually contracting section constitute the expansion-compression extrusion section of the die cavity. Among them, the ratio of the length L of the third tapered section to the inner diameter D of the sizing belt die cavity, L / D, is controlled between 1 and 3, so that the continuous expansion-compression extrusion die cavity has a short expansion cone and a long compression cone structure. Furthermore, step S2 also includes: controlling the temperature T2 at the junction of the first expanding section and the second contracting section to be higher than the temperature T1 at the expansion inlet and the outlet temperature T3 of the sizing zone.

2. The aluminum alloy coil / bar production process suitable for cold heading parts according to claim 1, characterized in that, A heating element is provided at the junction of the first expanding section and the second contracting section to achieve the goal that the temperature T2 at the junction of the first expanding section and the second contracting section is higher than the temperature T1 at the expansion inlet and the outlet temperature T3 of the sizing belt.

3. The aluminum alloy coil / bar production process suitable for cold heading parts according to claim 1 or 2, characterized in that, T2=480-540℃, T1=320-400℃, T3=280-340℃.

4. The aluminum alloy coil / bar production process suitable for cold heading parts according to claim 1 or 2, characterized in that, The inner diameter of the sizing belt mold cavity is D = 25-45mm, and the length of the third tapered section is L = (1~3)×D.

5. The aluminum alloy coil / bar production process suitable for cold heading parts according to claim 1 or 2, characterized in that, S3 includes: water quenching cooling treatment of the product extruded by differential temperature continuous expansion-compression and the mold cavity outlet.

6. The aluminum alloy coil / bar production process suitable for cold heading parts according to claim 5, characterized in that, The rapid cooling continuous casting in step S1 yields an aluminum alloy disc-shaped billet with a diameter of 20mm±0.5mm, which is then subjected to differential temperature continuous expansion-compression extrusion in step S2 to produce a round bar coil with a diameter of 25-45mm.

7. The aluminum alloy coil / bar production process suitable for cold heading parts according to claim 5, characterized in that, Step S4 includes: performing online roughening treatment on the surface of the product obtained by online quenching and cooling; Step S5 includes: performing online surface phosphating and lubrication treatment on the roughened product.

8. The aluminum alloy coil / bar production process suitable for cold heading parts according to claim 7, characterized in that, The online surface phosphating lubrication treatment includes phosphating-saponification treatment; the phosphating-saponification treatment process is as follows: the phosphating polymer lubricant is heated to a temperature maintained at 50-70℃, and dried after treatment for 30-120 seconds.

9. The aluminum alloy coil / bar production process suitable for cold heading parts according to claim 5, characterized in that, Step S6 includes: using a three-point bending wheel to roll the material clockwise or counterclockwise according to a preset weight or length.

10. An aluminum alloy coil / bar product suitable for cold heading of parts, prepared by the production process described in any one of claims 1-9.

Images