CN113293273B - Processing method of 2xxx series aluminum alloy bar and wire for fastener - Google Patents

Abstract

The invention discloses a processing method of 2xxx series aluminum alloy bars and wires for fasteners, which adopts an aluminum ingot to add intermediate alloy to be smelted in a smelting furnace, and then adopts semi-continuous casting to obtain an industrial cast ingot; homogenizing the ingot added with the alloy, heating the ingot to 480-505 ℃ from room temperature in a one-stage or multi-stage heating mode, and keeping the temperature for 10-60h; extruding the obtained cast ingot into a bar, controlling the speed of an extrusion outlet of the bar at 0.1-4mm/s and the extrusion temperature at 360-470 ℃; and (3) carrying out annealing heat treatment on the extruded bar blank, wherein the annealing process parameters are as follows: the temperature is 250-450 ℃, the annealing time is 0.5-3h, and the annealing bar is obtained after discharging and air cooling; performing cold drawing on the extruded bar or the extruded and annealed bar; carrying out solution quenching on the cold-drawn bar and wire; the rod and wire are pre-stretched, and the pre-stretching amount is controlled to be 0.1-3%.

Description

Processing method of 2xxx series aluminum alloy bar and wire for fastener

Technical Field

The invention belongs to the technical field of aluminum alloy processing, and particularly relates to a processing method of 2xxx series aluminum alloy bars and wires for fasteners.

Background

The fastener is used as a mechanical basic part, the using amount of the fastener on an airplane is the largest, the number of the fastener accounts for about 65% of the total amount of airplane parts, the weight of the fastener accounts for 5% of the weight of an airplane structure, and the total value of the fastener accounts for 10% -15% of the airplane structure. As a connecting piece of a host and a component, the fastening piece, the host and the component bear various requirements of basic performance and are suitable for occasions of high temperature, high pressure, low temperature, vibration, corrosion, heavy load, alternating stress, shearing resistance, torsion resistance and the like. The high-end fastener is used as an important connecting unit and has important application value. The materials used to make the fasteners must have stringent standards requirements, the quality and reliability of which play an important role in the operational performance and structural safety of the host machine.

The aluminum fastener has light weight, high specific strength and excellent corrosion resistance, and is widely applied to the aerospace field, such as bolts, studs, screws, nuts, washers, pins, rivets and the like. With the advancement of airplanes, higher weight reduction and performance requirements are placed on fasteners and materials thereof. Currently, aluminum alloy grades for threaded fasteners are mainly 2024-T4, 7075-T73 and 6061-T6. The rivet wire is represented by 2024, 2017, 2117, 7050 and other alloys. With the development of the aerospace industry, the development of aluminum alloy fasteners is developing towards the direction of matching the comprehensive properties of high strength, high toughness and corrosion resistance.

The high-strength aluminum alloy fastener in China is relatively late in development, has a large difference from foreign countries in the aspects of production, development and application, and easily generates defects of cracks, folding and the like in the shaping and forming process of the fastener processed in the later period, thereby greatly reducing the production efficiency of the fastener and increasing the production cost. The 2 xxx-series and 7 xxx-series aluminum alloys have high strength, but are not easily post-formed. The existing extrusion forming process can cause obvious coarse crystal layers to appear on the surface of the high-strength aluminum alloy material, and the coarse crystal structures on the surface have great harm to the forming performance and the corrosion performance of a fastener product. Therefore, the development of high-strength aluminum alloy materials for fasteners needs to control alloy components and microstructures, and the relationship among good strength, corrosion performance, toughness and formability is matched, so that the alloy has good formability while achieving high strength.

Patent CN201910747413.9 discloses a processing method of a high-strength aluminum alloy sleeve, and the alloy element proportion is as follows: 0.2-6wt% of Zn,0.2-6wt% of Mg,0.2-3wt% of Mn,0.2-4wt% of Cu,0.1-2wt% of Sc,0.1-2wt% of Yb,0.1-1wt% of Tb,0.2-2wt% of Zr and the balance of Al. According to the processing method of the high-strength aluminum alloy sleeve, the selected alloy components meet the requirements of tensile strength of more than 450MPa and hardness of more than 160HV after aging treatment. However, the patent adds rare earth micro-alloy elements such as Sc, yb and the like, so that the alloy cost is high and the processing technology is complex. Patent CN201710-458051.2 discloses a high-strength aluminum or aluminum alloy fastener and a preparation method thereof, wherein an angular bending channel is adopted for extrusion, and the obtained aluminum alloy material of the fastener has a grain size of below 2 μm, so that the mechanical property is remarkably improved while high molding is ensured. Patent CN201410712620.8 discloses a preparation process of high-performance fine-grained aluminum alloy wire and rod for aluminum bolt, which realizes grain refinement through continuous extrusion process, and the grain size can reach about 30 μm. However, the angular bent channel extrusion and continuous extrusion processing process is complex and is not suitable for the processing deformation mode of 2xxx series industrial large-scale cast ingots.

Disclosure of Invention

The invention provides a processing method of 2xxx series aluminum alloy bars and wires for fasteners by overcoming the defects of the prior art and optimizing alloy components and accurately controlling the processing technology. The 2xxx bars and wires processed by the method have high strength, good corrosion performance and forming performance, low production cost, and no volatile and other refractory alloy smelting components, so that the alloy smelting is simpler, and the preparation process method of the bars and wires is simpler.

The invention is realized by the following technical scheme.

A processing method of 2xxx series aluminum alloy bars and wires for fasteners comprises the following steps:

step (I): smelting an aluminum ingot added with intermediate alloy in a smelting furnace, and then obtaining an industrial cast ingot by adopting semi-continuous casting;

step (II): homogenizing the ingot added with the alloy, heating the ingot to 480-505 ℃ from room temperature in a one-stage or multi-stage heating mode, and keeping the temperature for 10-60h;

step (three): extruding the cast ingot obtained in the step (II) into a bar, controlling the speed of an extrusion outlet of the section bar to be 0.1-4mm/s and controlling the extrusion temperature to be 360-470 ℃;

step (IV): annealing heat treatment is carried out on the extruded bar blank, and the annealing process parameters are as follows: the temperature is 250-450 ℃, the annealing time is 0.5-3h, and the annealing bar is obtained after discharging and air cooling;

step (V): performing cold drawing on the extruded bar or the extruded and annealed bar;

step (six): carrying out solution quenching on the cold-drawn bar and wire at the solution temperature of 485-505 ℃ for 0.1-3h;

step (seven): the bar and the wire are pre-stretched, and the pre-stretching amount is controlled to be 0.1-3%.

Further, the aluminum alloy comprises the following components in percentage by weight: 3.8 to 4.9 percent of Cu, 1.2 to 1.8 percent of Mg, 0.3 to 0.9 percent of Mn0.5 percent, less than or equal to 0.5 percent of Cr, 0.01 to 0.15 percent of Ti, less than or equal to 0.5 percent of Fe, less than or equal to 0.5 percent of Si, less than or equal to 0.2 percent of Zn, and the balance of Al, and the alloy satisfies the following conditions: 5% < Cu + Mg <6.5%.

Further, in the step (II), the ingot heat-soaking process is carried out in a two-stage slow heating mode from room temperature, and comprises (1) a first-stage homogenization heat treatment process of low-temperature pre-precipitation and promotion of precipitation of dispersed phase AlCrMn; (2) A second-stage homogenization heat treatment process for eliminating high-melting-point Al2CuMg phase and Al2Cu phase in a long-term homogenization heat preservation process. The optimized homogenizing annealing heat treatment process promotes the dispersed phase to precipitate and pin the grain boundary, and inhibits the recrystallization and grain growth of the structure in the extrusion process.

Further, in the step (II), the ingot heat-soaking process is carried out in a two-stage slow heating mode from room temperature, the 2xxx aluminum alloy ingot is heated to 350-480 ℃ from room temperature at a heating rate of 5-100 ℃/h for 3-30h, the temperature is kept for 3-15 h, and then the 2xxx aluminum alloy ingot is heated to 480-505 ℃ at a heating rate of 1-30 ℃/h for 2-10h, and the temperature is kept for 0.5-60 h.

Further, the ingot extrusion temperature in the step (III) is controlled to be 400-450 ℃; the temperature of the extrusion cylinder is controlled to be 400-450 ℃, and the speed of the profile extrusion outlet is controlled to be 0.1-3mm/s; the extrusion is carried out at a high temperature and a low strain rate, so that the severe shearing deformation of the outer metal layer in the extrusion process is reduced, the tissue nonuniformity in the extrusion process is reduced, and the coarse crystal layer of the extruded product is effectively inhibited.

Further, annealing heat treatment is carried out on the extruded bar blank in the step (IV), and annealing process parameters are as follows: the temperature is 350-450 ℃, and the annealing time is 1-3h.

Further, the extruded bar blank or the extruded and annealed bar blank in the step (five) is subjected to multi-pass cold drawing and intermediate annealing, the final cold drawing deformation amount before quenching is controlled to be 20-40%, and the equivalent strain is controlled to be 0.23-0.5; by controlling the cold drawing deformation amount before quenching, enough recrystallization driving force is ensured in the subsequent solid solution process, and the final product structure is ensured to be a uniform fine crystal structure.

Further, the cold-drawn bar and wire are subjected to solution quenching in the step (six), the solution temperature is 485-500 ℃, and the temperature is kept for 0.5-3h. By controlling the solid solution temperature, the precipitation of coarse phases in the structure and second phases in the quenching process is inhibited, and the corrosion performance of the final material is improved.

Further, in the step (VII), the drawing amount of the bar and the wire is controlled to be 0.5-2.5%.

Furthermore, the average grain size of the bar and the wire after the solution treatment is 10-150 μm, and the section has no coarse crystal layer.

Furthermore, after T4 natural aging treatment, the yield strength of the bar and the wire is more than 300MPa, the tensile strength is more than 450MPa, and the elongation is more than 20%; in the T6 state, the yield strength is more than 360MPa, the tensile strength is more than 480MPa, and the elongation is more than 15%.

In the production process of the bars and the wires, a heat treatment system, an extrusion process system, such as ingot casting temperature, extrusion speed and the like, and a cold deformation and annealing process system can influence the microstructure and the mechanical property of a final product, so that reasonable and correct processing process parameters need to be selected in the production process of the bars and the wires.

The invention has the beneficial technical effects that:

(1) The invention comprehensively considers the influence effect of the microstructure on the material forming performance. The 2xxx series bar and wire prepared by the common process has a coarse grain structure and obvious coarse grain layer structure. The final structure performance, the size precision and the surface quality of the final 2xxx series alloy bar are controlled by the comprehensive matching of the extrusion process, the annealing process and the cold drawing deformation, so that the uniform microstructure with fine and uniform grain structure and no coarse crystal layer on the surface is finally obtained, the excellent matching of plasticity and mechanical property is realized, and the processing and forming performance of the 2xxx series aluminum alloy bar and wire for the fastener is effectively improved.

(2) The invention adopts multi-stage homogenization treatment, high-temperature solid solution rapid quenching heat treatment, stretching straightening and other processes in the process. A multi-stage homogenization heat treatment process is adopted, and the dispersed phase is promoted to be uniformly dispersed and precipitated at a low-temperature section in a slow heating mode; the heat soaking and preserving process in the high temperature section ensures that the coarse phase is melted back as much as possible, and improves the purity of the microstructure. Meanwhile, the high-temperature solid solution heating and the higher cooling rate are reasonably selected, so that the purity of the final microstructure of the material is effectively improved, the precipitation of a second phase in the quenching process is inhibited, and the comprehensive matching of the strength and the corrosion performance of the bar and the wire is ensured.

(3) By optimizing the alloy components and the processing technology, the finally prepared bar and wire has compact structure, fine crystal grains, the size of the crystal grains is 10-150 mu m, no coarse crystal layer exists on the section, and the comprehensive performance is excellent. After T4 natural aging treatment, the yield strength of the bar and the wire is more than 300MPa, the tensile strength is more than 450MPa, and the elongation is more than 20%; in the T6 state, the yield strength is more than 360MPa, the tensile strength is more than 480MPa, and the elongation is more than 15%.

(4) The invention has the advantages of simple alloy components, no need of adding rare earth elements, sc and other noble metal elements, simple casting process, simple preparation process, low cost and the like, and can be widely used as raw materials of fasteners.

In conclusion, the aluminum alloy rod and wire products prepared by the process have high mechanical property, excellent forming property and no coarse crystal layer, and are far higher than the alloy prepared by the conventional process.

Drawings

FIG. 1 is a flow chart of the manufacturing process of the rod and wire of the present invention;

FIG. 2 is a grain structure comparison of a 2xxx bar in longitudinal section;

FIG. 3 is a comparison of the three point bending properties of 2xxx bars;

FIG. 4 is a comparison of intergranular corrosion structures of bars in T4 state.

Detailed Description

The present invention will be described in detail with reference to the following embodiments.

Example 1

The aluminum alloy comprises the following components in percentage by weight: 4.18 percent of Cu, 1.48 percent of Mg, 0.6 percent of Mn, 0.02 percent of Cr0.02 percent of Ti, 0.02 percent of Fe, 0.07 percent of Si, 0.1 percent of Zn and the balance of Al. The specific production process is shown in figure 1, and the actual operation steps are as follows:

(1) Carrying out homogenization heat treatment on a phi 410mm ingot obtained by alloy semi-continuous casting, heating to 450 ℃ at a heating rate of 66 ℃/h, preserving heat for 5h, then heating to 498 ℃ at a heating rate of 10 ℃/h, preserving heat for 38h, and air cooling;

(2) Extruding the ingot after soaking, wherein the extrusion temperature is 430-440 ℃, and the extrusion speed is 0.4-0.8mm/min; firstly extruding the phi 410mm cast ingot to a phi 91mm bar, and then carrying out secondary extrusion to a phi 9.5mm bar;

(3) Drawing the extruded bar from a bar with the diameter of 9.5mm to a bar with the diameter of 8 mm;

(4) Carrying out solution heat treatment on the bar in the drawing state, and keeping the temperature at 495 ℃ for 1h;

(5) On-line quenching, with pre-stretching of 0.5%.

Example 2

The aluminum alloy comprises the following components in percentage by weight: 4.18 percent of Cu, 1.48 percent of Mg, 0.6 percent of Mn, 0.02 percent of Cr0.02 percent of Ti, 0.02 percent of Fe, 0.07 percent of Si, 0.1 percent of Zn and the balance of Al. The specific production process is shown in figure 1, and the actual operation steps are as follows:

(1) Carrying out homogenization heat treatment on a phi 410mm ingot obtained by alloy semi-continuous casting, heating to 450 ℃ at a heating rate of 66 ℃/h, preserving heat for 5h, then heating to 498 ℃ at a heating rate of 10 ℃/h, preserving heat for 38h, and air cooling;

(2) Extruding the ingot after soaking, wherein the extrusion temperature is 430-440 ℃, and the extrusion speed is 0.4-0.8mm/min; firstly extruding the phi 410mm cast ingot to a phi 91mm bar, and then carrying out secondary extrusion to a phi 10.4mm bar;

(3) Annealing, heat-treating and softening the extruded bar, wherein the annealing process is 350 ℃/1h;

(4) Drawing the extruded bar from a bar with the diameter of 10.4mm to a bar with the diameter of 9 mm;

(5) Carrying out solution heat treatment on the bar in the drawing state, and keeping the temperature at 495 ℃ for 1h;

(6) Quenching on line, and pre-stretching by 1.5 percent.

Example 3

The aluminum alloy comprises the following components in percentage by weight: 4.5 percent of Cu, 1.48 percent of Mg, 0.6 percent of Mn, 0.02 percent of Cr, 0.02 percent of Ti, 0.18 percent of Fe, 0.06 percent of Si, 0.1 percent of Zn and the balance of Al. The specific production process is shown in figure 1, and the actual operation steps are as follows:

(1) Carrying out homogenization heat treatment on a phi 410mm ingot obtained by alloy semi-continuous casting, heating to 450 ℃ at a heating rate of 66 ℃/h, preserving heat for 5h, then heating to 498 ℃ at a heating rate of 10 ℃/h, preserving heat for 38h, and air cooling;

(2) Extruding the ingot after soaking, wherein the extrusion temperature is 430-440 ℃, and the extrusion speed is 0.4-0.8mm/min; firstly extruding the phi 410mm cast ingot to a phi 91mm bar, and then carrying out secondary extrusion to a phi 9.2mm bar;

(3) Annealing, heat-treating and softening the extruded bar, wherein the annealing process is 400 ℃/1h;

(4) Drawing the extruded bar from a bar with the diameter of 9.2mm to a bar with the diameter of 8 mm;

(5) Carrying out solution heat treatment on the bar in the drawing state, and keeping the temperature at 495 ℃ for 1h;

(6) Quenching on line, and pre-stretching by 1.5 percent.

Example 4

The aluminum alloy comprises the following components in percentage by weight: 4.23 percent of Cu, 1.40 percent of Mg, 0.58 percent of Mn, 0.02 percent of Cr0.02 percent of Ti, 0.02 percent of Fe, 0.15 percent of Si, 0.05 percent of Zn, and the balance of Al. The specific production process is shown in figure 1, and the actual operation steps are as follows:

(1) Carrying out homogenization heat treatment on a phi 410mm ingot obtained by alloy semi-continuous casting, heating to 450 ℃ at a heating rate of 66 ℃/h, preserving heat for 5h, then heating to 498 ℃ at a heating rate of 10 ℃/h, preserving heat for 38h, and air cooling;

(2) Extruding the ingot after soaking, wherein the extrusion temperature is 430-440 ℃, and the extrusion speed is 0.4-0.8mm/min; firstly extruding the phi 410mm cast ingot to a phi 91mm bar, and then carrying out secondary extrusion to a phi 9.2mm bar;

(3) Annealing, heat-treating and softening the extruded bar, wherein the annealing process is 400 ℃/1h;

(4) Drawing the extruded bar from a bar with the diameter of 9.2mm to a bar with the diameter of 8 mm;

(5) Carrying out solution heat treatment on the bar in the drawing state, and keeping the temperature at 495 ℃ for 1h;

(6) On-line quenching, 2% prestretching.

Example 5

The aluminum alloy comprises the following components in percentage by weight: 4.23% of Cu, 1.40% of Mg, 0.58% of Mn, 0.02% of Cr0.02%, 0.02% of Ti, 0.15% of Fe, 0.05% of Si, 0.15% of Zn and the balance of Al. The specific production process is shown in figure 1, and the actual operation steps are as follows:

(1) Carrying out homogenization heat treatment on a phi 410mm ingot obtained by alloy semi-continuous casting, heating to 450 ℃ at a heating rate of 66 ℃/h, preserving heat for 5h, then heating to 498 ℃ at a heating rate of 10 ℃/h, preserving heat for 38h, and air cooling;

(2) Extruding the ingot after soaking, wherein the extrusion temperature is 430-440 ℃, and the extrusion speed is 0.4-0.8mm/min; firstly extruding the phi 410mm cast ingot to a phi 91mm bar, and then carrying out secondary extrusion to a phi 5mm bar;

(3) Annealing, heat-treating and softening the extruded bar, wherein the annealing process is 350 ℃/1h;

(4) Drawing the extruded bar from a bar with the diameter of 5mm to a wire with the diameter of 4 mm;

(5) Carrying out solution heat treatment on the bar in the drawing state, and keeping the temperature at 495 ℃ for 1h;

(6) Online quenching, and pre-stretching by 2 percent.

Comparative example 1

The aluminum alloy comprises the following components in percentage by weight: 4.18 percent of Cu, 1.48 percent of Mg, 0.6 percent of Mn, 0.02 percent of Cr0.02 percent of Ti, 0.02 percent of Fe, 0.07 percent of Si, 0.15 percent of Zn and the balance of Al. The specific production process is shown in figure 1, and the actual operation steps are as follows:

(1) Carrying out homogenization heat treatment on a phi 410mm ingot obtained by alloy semi-continuous casting, heating to 450 ℃ at a heating rate of 66 ℃/h, preserving heat for 5h, then heating to 498 ℃ at a heating rate of 10 ℃/h, preserving heat for 38h, and air cooling;

(2) Extruding the ingot after soaking, wherein the extrusion temperature is 430-440 ℃, and the extrusion speed is 0.4-0.8mm/min; firstly extruding the phi 410mm cast ingot to a phi 91mm bar, and then carrying out secondary extrusion to a phi 8mm bar;

(3) Carrying out solution heat treatment on the extruded bar, and keeping the temperature at 495 ℃ for 1h;

(4) Quenching on line, and pre-stretching by 2.5 percent.

Comparative example 2

The aluminum alloy comprises the following components in percentage by weight: 4.18 percent of Cu, 1.48 percent of Mg, 0.6 percent of Mn, 0.02 percent of Cr0.02 percent of Ti, 0.02 percent of Fe, 0.17 percent of Si, 0.07 percent of Zn, and the balance of Al. The specific production process is shown in figure 1, and the actual operation steps are as follows:

(1) Carrying out homogenization heat treatment on a phi 410mm ingot obtained by alloy semi-continuous casting, heating to 450 ℃ at a heating rate of 66 ℃/h, preserving heat for 5h, then heating to 498 ℃ at a heating rate of 10 ℃/h, preserving heat for 38h, and air cooling;

(2) Extruding the ingot after soaking, wherein the extrusion temperature is 430-440 ℃, and the extrusion speed is 0.4-0.8mm/min; firstly extruding the phi 410mm cast ingot to a phi 91mm bar, and then carrying out secondary extrusion to a phi 9.5mm bar;

(3) Drawing the extruded bar from a bar with the diameter of 9.5mm to a bar with the diameter of 8.7 mm;

(4) Carrying out solution heat treatment on the bar in the drawing state, and keeping the temperature at 495 ℃ for 1h;

(5) Drawing the extruded bar from a bar with the diameter of 8.7mm to a bar with the diameter of 8 mm;

(6) Pre-stretching for 1.5 percent;

comparative example 3

The aluminum alloy comprises the following components in percentage by weight: 4.23 percent of Cu, 1.40 percent of Mg, 0.58 percent of Mn, less than or equal to 0.5 percent of Cr, 0.01 to 0.15 percent of Ti, 0.15 percent of Fe, 0.05 percent of Si, 0.2 percent of Zn and the balance of Al. The specific production process is shown in figure 1, and the actual operation steps are as follows:

(1) Carrying out homogenization heat treatment on a phi 410mm ingot obtained by alloy semi-continuous casting, heating to 450 ℃ at a heating rate of 66 ℃/h, preserving heat for 5h, then heating to 498 ℃ at a heating rate of 10 ℃/h, preserving heat for 38h, and air cooling;

(2) Extruding the ingot after soaking, wherein the extrusion temperature is 430-440 ℃, and the extrusion speed is 0.4-0.8mm/min; firstly extruding a phi 410mm cast ingot to a phi 91mm bar, and then carrying out secondary extrusion to a phi 9.2mm bar;

(3) Annealing, heat-treating and softening the extruded bar, wherein the annealing process is 400 ℃/1h;

(4) Drawing the extruded bar from a bar with the diameter of 9.2mm to a bar with the diameter of 8 mm;

(5) Carrying out solution heat treatment on the bar in the drawing state, and keeping the temperature at 485 ℃ for 1h;

(6) Quenching on line, and pre-stretching by 1.5 percent.

Table 1 shows the performance indexes of the inventive alloy and the comparative alloy in different states T4 and T6 and the corresponding quantitative analysis results of the microstructure, including the depth of the coarse crystal layer and the average grain size. And maximum bending displacement of the different alloys. As shown in Table 1, the elongation of the material is greatly improved while the material has higher mechanical properties by reasonably controlling a processing process system, for example, the T4-state elongation of the 2xxx aluminum alloy in the embodiment is generally more than 20%, and the elongation is still maintained to be more than 14% after T6 supplement aging. The T4 state elongation is generally higher than in comparative examples 1, 2 and 3. In addition, the surfaces of the present examples have no coarse crystal layer, as shown in fig. 1, while in comparative example 1, the bar material subjected to direct solution treatment in an extruded state has a significant coarse crystal structure, and the depth of the coarse crystal layer is close to 3mm. Comparative example 1 the typical microstructure morphology was a coarse grain structure at the edge of the extruded bar, with coarse grains of about 1mm size, and a deformed fibrous structure at the center, with grains in fibrous distribution along the direction of deformation. In the present invention, it is found that the grain size of the aluminum alloy plays a dominant role in the bending properties of the material. Cracks tend to propagate along coarse recrystallized grain boundaries. The deformation coordination performance of coarse grains is poor, and dislocation is easy to accumulate, so that the later-stage processing forming performance is influenced. For the present invention, the grain structure is a fine crystal structure close to equiaxed, and the inter-grain cooperative deformation is easy. Therefore, the alloy of the invention has good formability.

TABLE 1 Performance indices of the alloys of the examples and comparative examples

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In fig. 2, (a) is comparative example 1, (b) is comparative example 2, and (c) is example 1, as can be seen from fig. 2, comparative example 2 adopts the secondary cold drawing process after solid solution, the obtained grain structure morphology is relatively elongated, and the bending performance of different processes is evaluated, and the result is shown in fig. 3. The maximum bending strength and the corresponding bending displacement of the material of the present invention are higher than those of the material of comparative example 2, which indicates that the material of the present invention has good formability. FIG. 4 shows the intergranular corrosion structure comparison of the T4-state bar, wherein (a) shows the intergranular corrosion structure of comparative example 1, and (b) shows the intergranular corrosion structure of example 3.

Meanwhile, the invention adopts the rapid quenching process of high-temperature two-stage soaking treatment, high-temperature solution heat treatment and matching, and the control of the heat treatment process ensures that the coarse phase content in the microstructure of the finally prepared 2xxx bars and wires is smaller, and the second phase precipitated in the quenching transfer process is less, so that the comprehensive matching of good strength and corrosion resistance can be obtained by comprehensive factor control. The presence of the coarse phase in the matrix also causes the toughness of the material to deteriorate, mainly because the coarse phase differs in position from the matrix, and tends to cause stress concentration at the interface between the coarse phase and the aluminum matrix, thereby causing cracks. And through the optimization of the soaking process, the content of coarse phases in the microstructure of the material is reduced, so that the toughness of the material is improved. In comparative example 3, the solid solution temperature was only 485 ℃, which directly resulted in insufficient alloying elements solid-dissolved in the aluminum matrix, and it can be seen that the strengths after the treatment of the T4 state and the T6 state were reduced by more than 20MPa compared to comparative example 3. FIG. 3 is a comparison of the intergranular corrosion microstructures of example 3 and comparative example 1, and it can be seen that the maximum depth of intergranular corrosion of comparative example 1 is 381 μm, while the maximum depth of intergranular corrosion of example 1 is 82 μm. Therefore, the 2 xxx-series rods and wires prepared by the invention have good intergranular corrosion resistance.

The invention comprehensively considers the influence effect of the microstructure on the material forming performance. The uniform microstructure with fine and uniform grain structure and no coarse crystal layer on the surface is finally obtained through the comprehensive matching of the extrusion process, the annealing process and the drawing deformation, and the excellent matching of the plasticity and the mechanical property is realized. Meanwhile, the invention adopts the processes of multi-stage homogenization treatment, high-temperature solid solution rapid quenching heat treatment, stretching straightening and the like in the process, effectively improves the purity of the final microstructure of the material, inhibits the precipitation of a second phase in the quenching process, and ensures the comprehensive matching of the strength and the corrosion performance of the bar and the wire. The finally prepared 2xxx series bars and wires have high strength, high toughness, corrosion resistance and good processing and forming performance, can be used for manufacturing high-performance aluminum alloy bolts and nuts, and can also be used for manufacturing high-performance rivets, high-strength connecting pieces and other aluminum alloy connecting piece products.

The above is only a specific application example of the present invention, and the protection scope of the present invention is not limited in any way. All the technical solutions formed by equivalent transformation or equivalent replacement fall within the protection scope of the present invention.

Claims (6)

1. A processing method of 2xxx series aluminum alloy bar and wire for fasteners is characterized by comprising the following steps:

step (one): adding an intermediate alloy into an aluminum ingot, smelting in a smelting furnace, and then obtaining an industrial ingot by adopting semi-continuous casting;

step (II): homogenizing the ingot added with the alloy; the soaking process of the cast ingot carries out heat treatment from room temperature in a two-stage slow heating mode, the 2xxx aluminum alloy cast ingot is heated to 350-480 ℃ from room temperature at the heating rate of 5-100 ℃/h for 3-30h, the temperature is kept for 3-15 h, then the 2xxx aluminum alloy cast ingot is heated to 480 ℃ or 498-505 ℃ at the heating rate of 1-30 ℃/h, the heating time is 2-10h, the temperature is kept for 0.5h or 38-60 h;

step (three): extruding the cast ingot obtained in the step (II) into a bar, controlling the speed of an extrusion outlet of the section bar to be 0.1-4mm/s, and controlling the extrusion temperature to be 360-470 ℃;

step (IV): annealing heat treatment is carried out on the extruded bar blank, and the annealing process parameters are as follows: the temperature is 250-400 ℃, the annealing time is 0.5-1h, and the bar is taken out of the furnace and air-cooled to obtain an annealed bar;

step (V): performing multi-pass cold drawing and intermediate annealing on the extruded bar or the extruded and annealed bar, wherein the final cold drawing deformation amount before quenching is controlled to be 20-40%, and the equivalent strain is controlled to be 0.23-0.5;

step (six): carrying out solution quenching on the rods and the wires subjected to cold drawing in the fifth step, wherein the solution temperature is 485-505 ℃, and keeping the temperature for 0.1-3h;

step (seven): pre-stretching the bar and the wire, wherein the pre-stretching amount is controlled to be 0.1-3%;

the aluminum alloy comprises the following components in percentage by weight: 3.8 to 4.9 percent of Cu, 1.2 to 1.48 percent of Mg, 0.3 to 0.9 percent of Mn, less than or equal to 0.5 percent of Cr, 0.01 to 0.15 percent of Ti0.5 percent of Fe, less than or equal to 0.5 percent of Si, less than or equal to 0.2 percent of Zn, and the balance of Al, and the alloy satisfies the following conditions: 5% < Cu + Mg <6.5%.

2. The method for processing the 2xxx series aluminum alloy rods and wires for the fasteners as claimed in claim 1, wherein the ingot extrusion temperature in the step (three) is controlled to be 400-450 ℃; the temperature of the extrusion cylinder is controlled to be 400-450 ℃, and the speed of the profile extrusion outlet is controlled to be 0.1-3mm/s.

3. The method for processing the 2xxx series aluminum alloy rods and wires for the fasteners as claimed in claim 1, wherein the step (six) is to perform solution quenching on the rods and wires after cold drawing, the solution temperature is 485-500 ℃, and the temperature is kept for 0.5-3h.

4. The method of processing a 2 xxx-series aluminum alloy rod or wire for fasteners as claimed in claim 1, wherein in said step (seventy), the amount of stretch of the rod or wire is controlled to be 0.5-2.5%.

5. The method of manufacturing a 2 xxx-series aluminum alloy rod or wire for a fastener as claimed in claim 1, wherein the average grain size of the rod or wire after solution treatment is 10-150 μm, and the cross-section has no coarse crystal layer.

6. The method for processing 2xxx series aluminum alloy bars and wires for fasteners according to claim 1, wherein the yield strength of the bars and wires after T4 natural aging treatment is more than 300MPa, the tensile strength is more than 450MPa, and the elongation is more than 20%;

in the T6 state, the yield strength is more than 360MPa, the tensile strength is more than 480MPa, and the elongation is more than 15%.

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