A processing method for T-shaped profiles

Abstract

The present invention discloses a processing method for T-shaped profiles, which includes the following steps: (1) Install a die in an extrusion cylinder; (2) Heat the die and the ingot; (3) Extrude the ingot, and the profile is extruded from the die hole; (4) The finished product is obtained after quenching and cold working the profile in step (3). In the present invention, a diversion pit is used to control the metal flow rate during the extrusion process, ensuring the microstructure and external dimensions of the product; through the coordinated control of the ingot heating temperature, the tooling heating temperature, the extrusion speed, etc., isothermal and constant-speed extrusion is achieved, ensuring a uniform microstructure of the product; a two-stage heat preservation system is adopted for quenching after extrusion, and the heating temperature of the high temperature is closer to the overburning temperature, which can obtain a higher supersaturation degree, making the solid solution more sufficient, and warm water quenching can effectively prevent quenching deformation; cold working generates plastic deformation, increasing the internal dislocation density, eliminating the stress and torsional deformation generated in the early stage; cryogenic treatment improves the stress relief effect and the intergranular corrosion resistance, and the depth of intergranular corrosion can be reduced by 30%.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum profile processing, and in particular to a processing method for T-shaped profiles. Background Art

[0002] Aluminum profiles are made of aluminum alloy as raw materials and are extruded into shape through a mold. They have the advantages of light weight, and excellent corrosion resistance in air, water, and many chemical systems. Also, due to the excellent workability and formability of aluminum profiles, they are widely used in many fields. The T-shaped profile in aluminum profiles is a commonly used structure and can be used for ceiling keels, edge trimming, joint closing, bead strips, seam pressing, guide rails, etc. Traditional profile production mostly uses ingots that meet national standards, ordinary molds, and conventional production processes. The ordinary mold is a flat mold, and the flow rate is controlled by the size of the working belt of the mold during use, making the mold repair difficult. Conventional production processes include general processes such as non-constant speed isothermal extrusion and single-stage quenching in heat treatment. The prior art can cause uneven product organization, the generation of coarse grains, and ultimately lead to uneven and low performance; during the extrusion process, deformation and twisting are serious, and high-precision dimensional control cannot be achieved in the later stage. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a processing method for T-shaped profiles. In this method, after extrusion using a mold, combined with water-cooled quenching, cold working, and cryogenic treatment, a finished product with good quality, stable dimensions, high mechanical properties, and uniform organization is obtained.

[0004] The technical solution adopted by the present invention to solve the technical problem is:

[0005] A processing method for T-shaped profiles, characterized in that it includes the following steps:

[0006] (1) Install a mold in the extrusion cylinder;

[0007] (2) Heat the mold and the ingot;

[0008] (3) Extrude the ingot, and extrude the profile through the mold hole;

[0009] (4) Quench and cold work the profile in step (3) to obtain a finished product.

[0010] Further: Four T-shaped extrusion holes are evenly distributed circumferentially on the mold body, and a diversion pit is provided on the end face of the mold body of each T-shaped extrusion hole.

[0011] Further: The step of heating the mold in step (2) is: preheat the extrusion mold and the extrusion cylinder to 400 - 440 °C; the heating rate is 80 - 200 °C / h.

[0012] Further: The ingot heating step described in step ⑵ is: Gradually heat the ingot to 400 - 440 °C, control the temperature difference between the head and tail of the ingot ≤ 30 °C; The heating rate is 30 - 50 °C / min.

[0013] Further: The speed of the extruded profile described in step ⑶ is 0.1 - 0.5 mm / s.

[0014] Further: The quenching process described in step ⑷ is: After the profile is extruded, heat it up to 488 - 492 °C and keep it warm for 30 min; Then continue to heat it up to 495 - 499 °C and keep it warm for 10 min; Quench it with warm water.

[0015] Further: The process of the cold working described in step ⑷ is:

[0016] Stretch the profile with a permanent plastic deformation rate of 1.0 - 3.0%.

[0017] Further: The stretching speed is 5 - 10 mm / s. When clamping the profile, ensure that the flat part of the profile is aligned; During stretching, adjust the twisting head to eliminate the stress and twisting deformation generated during extrusion.

[0018] Further: The value range of the stretching force is: The force is greater than the product of the yield strength of the material and the cross-sectional area of the material and less than the product of the tensile strength of the material and the cross-sectional area of the material.

[0019] Further: After cold working, perform cryogenic treatment on the profile. The process is: Put the cold-worked profile into liquid nitrogen for a period of time.

[0020] The technical effects achieved by the present invention are:

[0021] In the present invention, four extrusion holes are evenly distributed in the circumferential direction of the die body. A diversion pit is arranged on the end face of the die body where each extrusion hole is located. The diversion pit is used to control the metal flow rate during the extrusion process, ensuring the structure and external dimensions of the product; Through the coordinated control of the ingot heating temperature, the tooling heating temperature, the extrusion speed, etc., isothermal and constant-speed extrusion is achieved, ensuring the uniform structure of the product; After extrusion, double-stage heat preservation system is adopted for quenching. The heating temperature at high temperature is closer to the overburning temperature, which can obtain a higher supersaturation degree, making the solid solution more sufficient. Warm water quenching can effectively prevent quenching deformation; Cold working generates plastic deformation, increasing the internal dislocation density and eliminating the stress and twisting deformation generated in the early stage; Cryogenic treatment improves the stress relief effect and the intergranular corrosion resistance, and the intergranular corrosion depth can be reduced by 30%. Description of the Drawings

[0022] Figure 1 is the die assembly drawing of the present invention;

[0023] Figure 2 is the schematic diagram of the diversion pit;

[0024] Figure 3 is a comparison of intergranular corrosion depth. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the scope of protection of the present invention cannot be limited thereto.

[0026] A T-shaped profile processing method, as shown in the figure, the innovation of the present invention lies in:

[0027] Extrusion barrel and die Figure 1 As shown:

[0028] An extrusion shaft 1 is set inside the inner sleeve 2 of the extrusion cylinder, and an extrusion gasket 4 is set at the front of the extrusion shaft through a connecting pin 3. The extrusion gasket squeezes the heated ingot 5 toward the extrusion die 7. The extrusion die and die pad 8 are set in the die sleeve 6, and a front ring 10 and a rear ring 11 are set at the front of the die sleeve through a positioning pin 9.

[0029] The processing method comprises the following steps:

[0030] ⑴Install the mold in the extrusion cylinder;

[0031] ⑵Heating the mold and ingot;

[0032] ⑶ Extrusion ingot, extrusion profiles in the die hole;

[0033] (4) The profile of step (3) is quenched and cold-processed to obtain a finished product.

[0034] The mold structure described in step (1) is: four T-shaped extrusion holes 15 are evenly distributed circumferentially on the mold body, and a process hole 14 with a diameter of 1.50 mm is provided on the T-shaped extrusion hole. A diversion pit 13 is provided on the end face of the mold body of each T-shaped extrusion hole. The width of the diversion pit is the thickness of the profile plus 10 to 15 mm, the depth is 15 mm, the inlet cone angle is 3-10° (different angles control the flow rate); the effective size of the mold working band is 3-5 mm (different sizes control the flow rate), and the shrinkage rate of the extrusion hole size is 0.6-1.5% (the shrinkage rate is the ratio of the increase in the extrusion hole size based on the product size. Different alloys and specifications use different shrinkage rates. In the invention, the profile thickness part is 0.7%, and the shape part is 1.2%.).

[0035] ① Preheat the mold and heat the mold and extrusion barrel to 400-440℃; the heating rate is 80-200℃ / h.

[0036] ② Gradual heating of the ingot; gradient heating of the ingot to 400-440°C, controlling the temperature difference between the head and tail of the ingot to be ≤30°C; heating rate of 30-50°C / min.

[0037] ③Load the preheated ingot into the extrusion cylinder for extrusion. The extrusion shaft pushes the ingot forward through the extrusion pad to complete upsetting, and then continues to move forward to extrude the ingot from the four extrusion holes. The extrusion speed is 0.1 - 0.5 mm / s to obtain four T-shaped aluminum alloy profiles.

[0038] A diversion pit is opened on the mold body, which can control the metal flow rate during extrusion and connect the front end of the product to the tail end of the previous product at the same time. The connection between the front end and the tail end is as follows: after the previous extrusion is completed, the upset is cut off, and there is metal remaining in the diversion pit. Then when the next product is extruded, the new metal will be mixed and welded with the metal in the diversion pit, thus realizing the head-to-tail connection of two connected products. Since the head and tail of the product are connected, the weight of the previous product will limit the free movement of the head end of the next product, including twisting, bending, etc., thereby improving the external dimensions of the product, reducing the twisting deformation at the front end of the product, and improving the yield rate and the tissue uniformity of the product.

[0039] The quenching process described in step ⑷ is as follows: after the profile is extruded, it is heated up uniformly for 20 min, heated up to 488 - 492 °C, and kept warm for 30 min; then it is heated up uniformly for 5 min, heated up to 495 - 499 °C, and kept warm for 10 min; quenching is carried out using warm water (30 - 38 °C). The heating temperature after the profile is extruded is closer to the overburning temperature, which can obtain a higher supersaturation degree, make the solid solution more sufficient, and warm water quenching can effectively prevent quenching deformation.

[0040] The cold working process described in step ⑷ is:

[0041] Apply a tensile force to the product, and the tensile force is greater than (yield strength of the material) R p0.2 × (cross-sectional area) F and the tensile force is less than (tensile strength of the material) R m × (cross-sectional area) F.

[0042] The tensile deformation exceeds the yield limit of the metal. The tensile deformation exceeds the yield limit of the metal: generally specified as a 0.2% permanent deformation occurs, and the tensile force exceeds (yield strength of the material) R p0.2 × (cross-sectional area) F, and reaches a permanent plastic deformation degree of 1.0 - 3.0%, so that the elastic recovery ability of each longitudinal fiber tends to be consistent, and the residual bending amount at each place after elastic recovery does not exceed the allowable value (the allowable value is generally divided into ordinary grade, high-precision grade and ultra-high-precision grade, and the required camber for each grade is also related to the circumscribed circle diameter of the product and the minimum wall thickness of the profile).

[0043] Adopt a permanent plastic deformation rate of 2.2 - 2.4%, control the equilibrium shift of stretching, maintain a slow stretching speed of 5 - 10 mm / s, ensure that the flat part of the profile is aligned when clamping the material, observe the twist change of the profile during stretching and rotate to adjust the twist head to eliminate the stress and twist deformation generated during extrusion and quenching, significantly improve the intergranular corrosion performance, determine the rotation amount according to the twist degree of the profile. Since the twist degree of each profile is different, the rotation amount is also different. Cold working produces plastic deformation, increases the internal dislocation density, and eliminates the stress and twist deformation generated in the early stage.

[0044] After cold working, the profile is subjected to cryogenic treatment. The process is as follows: The cold-worked profile is placed in liquid nitrogen at -150 to -180 °C and kept warm for 30 min. After cryogenic treatment, the internal stress of the material can be significantly improved, and its stress relief effect and the ability to improve intergranular corrosion resistance are obvious. As shown in Figure 3, in the present invention ( Figure 3a ) the maximum intergranular corrosion depth is 0.097 mm, which is more than 30% lower than the technical requirement value of 0.150 mm ( Figure 3b ).

[0045] The comprehensive mechanical properties of the prepared finished product are detected. Table 1 shows the comparison between the product of the present invention and the standard, and Table 2 shows the comparison between the product of the present invention and other products. Tensile strength Rm, yield strength R p0.2 , elongation after fracture A.

[0046] Control standard: Performance index <![CDATA[R p0.2 / MPa]]> Rm / MPa A / ％ GJB 2507A-2015 ≥290 ≥395 ≥10 The present invention 366 472 13

[0047] Table 1: Comparison between the present invention and the standard

[0048] As can be seen from Table 1, compared with the national military standard, the tensile strength of the present invention is increased by 19%, the specified non-proportional extension length is increased by 26%, and the elongation is increased by 30%.

[0049]

[0050] Table 2: Comparison between the present invention and other products.

Claims

1. A processing method for T-shaped profiles, characterized in that: It includes the following steps: (1) Install a die in the extrusion cylinder; (2) Heat the die and the ingot; (3) Extrude the ingot, and extrude the profile through the die hole; (4) After quenching and cold working the profile in step (3), obtain the finished product; The die structure described in step (1) is: Four T-shaped extrusion holes are evenly distributed circumferentially on the die body. A diversion pit is provided on the end face of the die body of each T-shaped extrusion hole. The width of the diversion pit is the profile thickness plus 10 to 15 mm, the depth is 15 mm, and the inlet cone angle is 3 - 10º; The steps of die heating described in step (2) are: Preheat the extrusion die and the extrusion cylinder to 400 - 440°C; The heating rate is 80 - 200°C / h; The steps of ingot heating described in step (2) are: Gradually heat the ingot to 400 - 440°C, and control the temperature difference between the head and the tail of the ingot ≤ 30°C; The heating rate is 30 - 50°C / min; The extrusion speed of the profile described in step (3) is 0.1 - 0.5 mm / s; The quenching process described in step (4) is: After the profile is extruded, heat it up to 488 - 492°C and hold for 30 min; Continue to heat it up to 495 - 499°C and hold for 10 min; Quench with warm water; The process of cold working described in step (4) is: Stretch the profile with a permanent plastic deformation rate of 1.0 - 3.0%; The stretching speed is 5 - 10 mm / s. When clamping the profile, ensure that the flat part of the profile is aligned; Adjust the twisting head during stretching to eliminate the stress and twisting deformation generated during extrusion; The value range of the stretching force is: The force is greater than the product of the yield strength of the material and the cross-sectional area of the material and the force is less than the product of the tensile strength of the material and the cross-sectional area of the material; After cold working, perform cryogenic treatment on the profile. The process is: Put the cold-worked profile into liquid nitrogen for a period of time.

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