Multi-stage finished annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner container and application thereof

Abstract

The present application relates to the technical field of cooking utensils, and provides a multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy used in rice cookers and application thereof, which comprises the following steps: after the 3003 aluminum alloy cold-rolled slab is kept at a first annealing temperature of 460-480 DEG C, the slab is kept at a second annealing temperature of 300-340 DEG C. According to the method, after the cold-rolled slab obtained after the cold-rolling process is kept at 460-480 DEG C, the slab is kept at 300-340 DEG C, the high mechanical property and high forming property of the cast-rolled slab are considered by optimizing the finished product annealing process, and the obtained cast-rolled 3003 aluminum alloy finished product is particularly suitable for application in the rice cooker inner container.

Description

Technical Field

[0001] This invention relates to the field of cookware technology, and in particular to a multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner pots and its application. Background Technology

[0002] Aluminum alloys can be classified according to their composition into: 1XXX series (industrial pure aluminum), 2XXX series (Al-Cu alloy), 3XXX series (Al-Mn alloy), 4XXX series (Al-Si alloy), 5XXX series (Al-Mg alloy), 6XXX series (Al-Mg-Si alloy), and 7XXX series (Al-Zn alloy). Alloys with different compositions have significantly different applications and fields of use. Among them, 3003 aluminum alloy belongs to the 3XXX series Al-Mn alloy, possessing excellent formability and corrosion resistance, and is widely used in the cookware industry, including rice cooker inner pots. The forming processes for 3003 aluminum alloy include hot rolling and casting rolling. Hot rolling involves first casting a thick ingot, then performing hot rolling and cold rolling sequentially to ultimately produce a sheet of the target thickness. Casting rolling, on the other hand, uses a casting rolling process to prepare a slab, which is then subjected to multiple cold rolling passes to finally become a finished cast-rolled sheet of the required thickness. Compared to hot rolling, casting rolling shortens the forming process and has a greater cost advantage, which has led to the increasing market share of 3003 aluminum alloy cast-rolled sheets in the cookware industry year by year.

[0003] The high Mn content in 3003 aluminum alloy, coupled with the rapid cooling rate of the cast-rolled sheet during forming, leads to severe segregation. Furthermore, the unavoidable presence of Fe and Si impurities in 3003 aluminum alloy results in a large number of AlMn binary, AlMnFe ternary, and AlMnFeSi quaternary phases within the microstructure. Although the second phase is somewhat fragmented after cold rolling, its size and morphology remain relatively coarse, easily becoming stress concentration crack initiation points during deep drawing, leading to poor mechanical and formability properties. Simultaneously, due to the unidirectional nature of cold rolling deformation, the microstructure of the cold-rolled sheet exhibits significant anisotropy, resulting in substantial differences in properties along the rolling direction, at 45° to the rolling direction, and perpendicular to the rolling direction, further weakening the material's formability. Summary of the Invention

[0004] This invention provides a multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner pots and its application. After the cold rolling process, the resulting cold-rolled slab is kept at 460-480℃ and then at 300-340℃. By optimizing the finished product annealing process, both high mechanical properties and high formability of the cast-rolled slab are achieved.

[0005] In a first aspect, the present invention provides a multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner pots, comprising:

[0006] After holding the 3003 aluminum alloy cold-rolled slab at a first-stage annealing temperature of 460–480℃, it is then held at a second-stage annealing temperature of 300–340℃.

[0007] According to the multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy for rice cooker inner pot provided by the present invention, the holding time of the first-stage annealing temperature is 0.5 to 2 hours; and the holding time of the second-stage annealing temperature is 2 to 6 hours.

[0008] According to the multi-stage finished product annealing method of cast-rolled 3003 aluminum alloy for rice cooker inner pot provided by the present invention, the first-stage annealing temperature is denoted as T1 (°C), the second-stage annealing temperature is denoted as T2 (°C), and the thickness of the 3003 aluminum alloy cold-rolled slab is denoted as H (mm).

[0009] The heating rate of the 3003 aluminum alloy cold-rolled slab to the first-stage annealing temperature is:

[0010]

[0011] And / or, the cooling rate from the primary annealing temperature to the secondary annealing temperature is

[0012]

[0013] According to the multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy for rice cooker inner pot provided by the present invention, the thickness of the 3003 aluminum alloy cold-rolled slab is 1-2.5 mm.

[0014] The multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy for rice cooker inner pots provided by the present invention includes:

[0015] The 3003 aluminum alloy cold-rolled slab is obtained by cold rolling a cast and rolled 3003 aluminum alloy slab to the specified thickness; the cold rolling includes a deformation amount of 10% to 20% of the current thickness per pass.

[0016] According to the multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy for rice cooker inner pot provided by the present invention, intermediate annealing is not performed in the cold rolling process.

[0017] According to the multi-stage finished product annealing method of cast-rolled 3003 aluminum alloy for rice cooker inner pot provided by the present invention, the cold-rolled slab of cast-rolled 3003 aluminum alloy is held at the first-stage annealing temperature, then held at the second-stage annealing temperature, and then cooled to obtain the finished product of cast-rolled 3003 aluminum alloy for rice cooker inner pot; the cooling includes: air cooling.

[0018] Secondly, the present invention also provides a finished product of cast-rolled 3003 aluminum alloy for rice cookers, obtained by the multi-stage finished product annealing method of cast-rolled 3003 aluminum alloy for rice cookers as described above.

[0019] According to the present invention, the cast-rolled 3003 aluminum alloy finished product for rice cooker inner pot has a yield strength ≥45MPa, tensile strength ≥115MPa, elongation ≥35%, and plastic strain ratio ≥0.65.

[0020] Thirdly, the present invention also provides the application of the cast-rolled 3003 aluminum alloy finished product for rice cooker inner pot as described above in rice cooker inner pot.

[0021] This invention provides a multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner pots and its application. After the cold rolling process, the cold-rolled slab is kept at 460-480℃ and then at 300-340℃. The mechanical properties and formability of the cast-rolled slab are improved by optimizing the finished product annealing process.

[0022] Specifically, the cast-rolled sheet obtained by the present invention has an average yield strength greater than or equal to 45 MPa, an average tensile strength greater than or equal to 115 MPa, an average elongation greater than or equal to 35%, and an average plastic strain ratio greater than or equal to 0.65 in the rolling direction, in the direction at 45° to the rolling direction, and in the direction perpendicular to the rolling direction. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a microstructure diagram of the cast plate obtained in Example 1 of the present invention;

[0025] Figure 2 This is a microstructure diagram of the cast plate obtained in Example 2 of the present invention;

[0026] Figure 3 This is a microstructure diagram of the cast plate obtained in Comparative Example 1 provided by the present invention.

[0027] Figure 4 This is a microstructure diagram of the cast plate obtained in Comparative Example 2 provided by the present invention.

[0028] Figure 5 This is a microstructure diagram of the cast plate obtained in Comparative Example 3 provided by the present invention.

[0029] Figure 6 This is a microstructure diagram of the cast plate obtained in Comparative Example 4 provided by the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] The following is combined with Figures 1-6 This invention describes a multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner pots and its application.

[0032] During the cold rolling process of cast-rolled 3003 aluminum alloy, work hardening becomes increasingly pronounced with increasing deformation, leading to increased processing difficulty and internal stress, and exacerbating the risk of sheet cracking during rolling. Therefore, intermediate annealing is typically required to release internal stress and soften the sheet, reducing deformation difficulty. After the final cold rolling pass, finished product annealing is necessary. By controlling the composition and microstructure, the mechanical properties, formability, and other properties of the product are coordinated and unified. For cast-rolled 3003 aluminum alloy, the significance of finished product annealing includes the following aspects: removing internal stress and reducing the possibility of cracking when the sheet is stamped into an inner liner; improving the morphology of the second phase, reducing its size, and decreasing the number of coarse second phases; promoting Mn atom diffusion and mitigating segregation; and controlling the microstructure, allowing for complete or partial recrystallization of the deformed microstructure according to the required strength and plasticity.

[0033] Considering the characteristics of the rice cooker inner pot's stamping process, it is necessary to ensure the relative uniformity of deformation in different directions of the sheet material, that is, to improve the uniformity of the material's properties in the rolling direction, perpendicular to the rolling direction, and at a 45° angle to the rolling direction. Considering the usage characteristics of the rice cooker inner pot, while ensuring high plasticity, a certain level of strength must also be guaranteed to reduce potential damage to the product surface caused by the production process, logistics process, and usage process.

[0034] This invention delves into the annealing process of finished products, discovering that short-term holding at 460–480℃ for cast-rolled 3003 aluminum alloy can promote solute atom diffusion, reduce the size of the second phase, and facilitate the transformation of edges from angular to smooth by preventing excessive grain growth. This improves mechanical properties and hardness, ensuring the strength of the pot body. It can also promote the transformation of the AlFeMn phase to the AlFeMnSi phase, thus enhancing formability. Subsequent cooling to 300–340℃ and holding for a longer period effectively removes internal stress from the cold-rolled sheet, reducing the possibility of cracking during subsequent deep drawing of the pot body. Furthermore, it promotes the diffusion of solute elements to mitigate segregation. Depending on the Mn content in the 3003 aluminum alloy, the temperature at which the cold-rolled structure recovers and recrystallizes is approximately between 260–340℃. Setting the secondary annealing temperature to 300–340℃ promotes the rapid transformation of the deformed structure into a relatively uniform recrystallized structure, thereby improving the uniformity of properties and ultimately enhancing the deep-drawing formability of the sheet.

[0035] Specifically, a multi-stage annealing method for a rice cooker inner pot made of cast-rolled 3003 aluminum alloy includes: holding the cold-rolled slab of cast-rolled 3003 aluminum alloy at a first-stage annealing temperature of 460-480℃, and then holding it at a second-stage annealing temperature of 300-340℃.

[0036] Preferably, the holding time at the primary annealing temperature is 0.5 to 2 hours; and / or, the holding time at the secondary annealing temperature is 2 to 6 hours.

[0037] The annealing time can be fine-tuned according to the composition of the aluminum alloy. For example, if the content of alloying elements is high, the annealing holding time can be appropriately extended.

[0038] The annealing of the finished product in this invention is carried out continuously. The heating rate and cooling rate have a substantial impact on the anisotropy of the microstructure of the cast-rolled plate of this invention. According to the experiment, the first-stage annealing temperature is denoted as T1 (°C), the second-stage annealing temperature is denoted as T2 (°C), and the thickness of the 3003 aluminum alloy cold-rolled slab is denoted as H (mm).

[0039] The heating rate of the 3003 aluminum alloy cold-rolled slab to the first-stage annealing temperature is:

[0040]

[0041] And / or, the cooling rate from the primary annealing temperature to the secondary annealing temperature is

[0042]

[0043] Preferably, the value of H is 1 to 2.5 mm.

[0044] Preferably, the multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner pots further includes:

[0045] The 3003 aluminum alloy cold-rolled slab is obtained by cold rolling a cast and rolled 3003 aluminum alloy slab to the specified thickness; the cold rolling includes a deformation amount of 10% to 20% of the current thickness per pass.

[0046] Preferably, the thickness of the cast-rolled 3003 aluminum alloy slab is 9-15 mm.

[0047] The aforementioned current thickness refers to the thickness of the sheet material to be cold-rolled during each cold rolling pass. That is, the deformation amount per pass is determined by the sheet thickness measured during cold rolling. Preferably, the cold rolling deformation amount per pass is 10-20%, which significantly reduces internal stress by minimizing the degree of deformation, ensuring smooth cold rolling even without intermediate annealing.

[0048] Preferably, intermediate annealing is not performed during the cold rolling process.

[0049] Preferably, the cold-rolled slab of the cast-rolled 3003 aluminum alloy is held at the first-stage annealing temperature, then held at the second-stage annealing temperature, and then cooled to obtain the finished cast-rolled 3003 aluminum alloy for rice cooker inner pot; the cooling includes air cooling.

[0050] The rice cooker inner pot is a finished product of cast-rolled 3003 aluminum alloy, prepared by the multi-stage finished product annealing method of cast-rolled 3003 aluminum alloy as described above.

[0051] The resulting cast-rolled 3003 aluminum alloy inner pot exhibits high uniformity in performance in the rolling direction, perpendicular to the rolling direction, and at a 45° angle to the rolling direction. Its average yield strength in these three directions is greater than or equal to 41 MPa, average tensile strength is greater than or equal to 110 MPa, average elongation is greater than or equal to 35%, and average plastic strain ratio is greater than or equal to 0.61. Preferably, the cast-rolled 3003 aluminum alloy inner pot has an average yield strength greater than or equal to 45 MPa, average tensile strength greater than or equal to 115 MPa, average elongation greater than or equal to 35%, and average plastic strain ratio greater than or equal to 0.65.

[0052] Moreover, in the rolling direction, perpendicular to the rolling direction, and at a 45° angle to the rolling direction, the cast-rolled 3003 aluminum alloy finished product for the rice cooker inner pot can achieve a yield strength ≥45MPa, a tensile strength ≥115MPa, an elongation ≥35%, and a plastic strain ratio ≥0.65.

[0053] As mentioned above, the application of cast-rolled 3003 aluminum alloy finished products in rice cooker inner pots;

[0054] Preferably, the inner pot of the rice cooker is made from cast and rolled 3003 aluminum alloy through a stamping process.

[0055] Where specific techniques or conditions are not specified in the examples, they shall be performed in accordance with the techniques or conditions described in the literature in this field, or in accordance with the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased through legitimate channels.

[0056] The 12mm thick 3003 aluminum alloy cast and rolled plate blank in this embodiment of the invention comprises: Al, 1.24% Mn, 0.15% Cu, 0.42% Si, and 0.37% Fe.

[0057] The 10mm thick 3003 aluminum alloy cast and rolled plate blank in this embodiment of the invention comprises: Al, 1.06% Mn, 0.12% Cu, 0.49% Si, and 0.31% Fe.

[0058] Example 1

[0059] A method for preparing a rice cooker inner pot using 3XXX series aluminum alloy cast-rolled sheet, comprising the following steps:

[0060] (1) A 3003 aluminum alloy cast and rolled plate blank with a thickness of 12mm is cold rolled to a thickness of 1.6mm in 9 passes; wherein the deformation amount of each pass is about 20%.

[0061] (2) The sheet obtained in step (1) is annealed. The annealing process is as follows: the sheet is placed in an annealing furnace and heated to the first-stage annealing temperature of 465℃ at a heating rate of 540℃ / h, held for 2 hours, and then cooled to the second-stage annealing temperature of 330℃ at a cooling rate of 170℃ / h, held for 5 hours, and the annealing is completed.

[0062] (3) Air cooling yields the finished cast-rolled sheet material.

[0063] The obtained cast-rolled sheet was tested. The testing process included: selecting tensile samples in the rolling direction, at 45° to the rolling direction, and perpendicular to the rolling direction of the cast-rolled sheet, and conducting mechanical property and plastic strain ratio tests. The plastic strain ratio was evaluated using (r0+2r45+r90) / 4, where r0 is the plastic strain ratio in the rolling direction, r45 is the plastic strain ratio at 45° to the rolling direction, and r90 is the plastic strain ratio perpendicular to the rolling direction. The test results are shown in Table 1 below.

[0064] Table 1

[0065]

[0066] The microstructure of the obtained cast-rolled sheet metal was observed, and the results are as follows: Figure 1As shown, the second phase in the tissue is small in size and uniformly dispersed, with no large-sized, sharp-edged second phase present.

[0067] Example 2

[0068] A method for preparing a rice cooker inner pot using 3XXX series aluminum alloy cast-rolled sheet, comprising the following steps:

[0069] (1) A 3003 aluminum alloy cast and rolled plate blank with a thickness of 10mm is cold rolled to a thickness of 2mm in 10 passes, wherein the deformation amount of each pass is about 15%.

[0070] (2) The sheet obtained in step (1) is subjected to finished product annealing. The finished product annealing process is as follows: the round sheet is placed in the annealing furnace and heated to the first-stage annealing temperature of 480℃ at a heating rate of 600℃ / h, held for 1h, and then cooled to the second-stage annealing temperature of 320℃ at a cooling rate of 230℃ / h, held for 6h, and the annealing is completed.

[0071] (3) Air cooling yields the finished cast-rolled sheet material.

[0072] The obtained cast-rolled sheet was tested. The testing process included selecting tensile samples in the rolling direction, at 45° to the rolling direction, and perpendicular to the rolling direction of the cast-rolled sheet, and conducting mechanical property and plastic strain ratio tests. The test results are shown in Table 2 below.

[0073] Table 2

[0074]

[0075] The microstructure of the obtained cast-rolled sheet metal was observed, and the results are as follows: Figure 2 As shown, the second phase in the tissue is small in size and uniformly dispersed, with no large-sized, sharp-edged second phase present.

[0076] Example 3

[0077] The process is basically the same as in Example 2, except that the annealing process of the finished product is replaced by: placing the aluminum plate in an annealing furnace, heating it to the first-stage annealing temperature of 480°C at a heating rate of 590°C / h, holding it at that temperature for 1 hour, and then cooling it to the second-stage annealing temperature of 320°C at a cooling rate of 230°C / h and holding it at that temperature for 6 hours to end the annealing process.

[0078] Example 4

[0079] The process is basically the same as in Example 2, except that the annealing process of the finished product is replaced by: placing the disc in an annealing furnace, heating it to the first-stage annealing temperature of 480°C at a heating rate of 600°C / h, holding it at that temperature for 1 hour, and then cooling it to the second-stage annealing temperature of 320°C at a cooling rate of 210°C / h and holding it at that temperature for 6 hours to end the annealing process.

[0080] Example 5

[0081] The process is basically the same as in Example 2, except that the annealing process of the finished product is replaced by: placing the disc in an annealing furnace, heating it to the first-stage annealing temperature of 480°C at a heating rate of 625°C / h, holding it at that temperature for 1 hour, and then cooling it to the second-stage annealing temperature of 320°C at a cooling rate of 230°C / h and holding it at that temperature for 6 hours to end the annealing process.

[0082] Example 6

[0083] The discs were placed in an annealing furnace and heated to the primary annealing temperature of 480℃ at a heating rate of 600℃ / h, held for 1 hour, and then cooled to the secondary annealing temperature of 320℃ at a cooling rate of 240℃ / h, held for 6 hours to complete the annealing process.

[0084] The finished cast-rolled plates obtained in Examples 3 to 6 were tested, and the test results are shown in Tables 3 to 6 below.

[0085] Table 3 Yield Strength (MPa)

[0086] Example 3 Example 4 Example 5 Example 6 Rolling direction 44 43 43 42 45° to the rolling direction 45 42 45 43 Perpendicular to the rolling direction 43 39 43 43 average value 44 41.3 43.7 42.7

[0087] Table 4 Tensile Strength (MPa)

[0088] Example 3 Example 4 Example 5 Example 6 Rolling direction 115 112 115 115 45° to the rolling direction 117 111 114 113 Perpendicular to the rolling direction 114 107 115 114 average value 115.3 110 114.7 114

[0089] Table 5. Elongation Rate (%)

[0090] Example 3 Example 4 Example 5 Example 6 Rolling direction 36 35 34 37 45° to the rolling direction 37 38 38 36 Perpendicular to the rolling direction 38 34 39 35 average value 37 35.7 37 36

[0091] Table 6 Plastic strain ratio (r)

[0092] Example 3 Example 4 Example 5 Example 6 Rolling direction 0.67 0.6 0.66 0.63 45° to the rolling direction 0.64 0.63 0.63 0.64 Perpendicular to the rolling direction 0.66 0.58 0.65 0.65 average value 0.65 0.61 0.64 0.64

[0093] As can be seen from Examples 2 to 6, optimizing the annealing process (heating rate and cooling rate) in Example 2 can take into account both the strength and plasticity of the plate, ensuring that its yield strength, tensile strength, elongation and plastic strain ratio are higher than 45MPa, 115MPa, 35% and 0.65, respectively.

[0094] Comparative Example 1

[0095] The process is basically the same as in Example 1, except that the annealing process of the finished product is replaced by placing the disc in an annealing furnace and heating it to the annealing temperature of 360°C at a heating rate of 600°C / h and holding it at that temperature for 7 hours.

[0096] The obtained cast-rolled sheet was tested. The testing process included selecting tensile samples in the rolling direction, at 45° to the rolling direction, and perpendicular to the rolling direction of the cast-rolled sheet, and conducting mechanical property and plastic strain ratio tests. The test results are shown in Table 7 below.

[0097] Table 7

[0098]

[0099] The microstructure of the obtained cast-rolled sheet metal was observed, and the results are as follows: Figure 3 As shown, the second phase in the tissue is less numerous and larger in size, and there is local aggregation.

[0100] Comparative Example 2

[0101] The process is basically the same as in Example 2, except that the annealing process of the finished product is replaced by placing the disc in an annealing furnace and heating it to the annealing temperature of 480°C at a heating rate of 600°C / h, holding it at that temperature for 1 hour, and then ending the annealing process.

[0102] The obtained cast-rolled sheet was tested. The testing process included selecting tensile samples in the rolling direction, at 45° to the rolling direction, and perpendicular to the rolling direction of the cast-rolled sheet, and conducting mechanical property and plastic strain ratio tests. The test results are shown in Table 8 below.

[0103] Table 8

[0104]

[0105]

[0106] The microstructure of the obtained cast-rolled sheet metal was observed, and the results are as follows: Figure 4 As shown, the second phase in the tissue is relatively large in size and exhibits local aggregation.

[0107] Comparative Example 3

[0108] The process is basically the same as in Example 2, except that the annealing process of the finished product is replaced by placing the disc in an annealing furnace and heating it to the annealing temperature of 480°C at a heating rate of 600°C / h, holding it at that temperature for 7 hours, and then ending the annealing process.

[0109] The obtained cast-rolled sheet was tested. The testing process included selecting tensile samples in the rolling direction, at 45° to the rolling direction, and perpendicular to the rolling direction of the cast-rolled sheet, and conducting mechanical property and plastic strain ratio tests. The test results are shown in Table 9 below.

[0110] Table 9

[0111]

[0112] The microstructure of the obtained cast-rolled sheet metal was observed, and the results are as follows: Figure 5 As shown, the second phase in the tissue is abnormally large and aggregates locally.

[0113] Comparative Example 4

[0114] The process is basically the same as in Example 2, except that the annealing process of the finished product is replaced by placing the disc in an annealing furnace and heating it at a rate of 600°C / h to the annealing temperature of 320°C and holding it there for 6 hours to end the annealing process.

[0115] The obtained cast-rolled sheet was tested. The testing process included selecting tensile samples in the rolling direction, at 45° to the rolling direction, and perpendicular to the rolling direction of the cast-rolled sheet, and conducting mechanical property and plastic strain ratio tests. The test results are shown in Table 10 below.

[0116] Table 10

[0117]

[0118] The microstructure of the obtained cast-rolled sheet metal was observed, and the results are as follows: Figure 6 As shown, the second phase in the tissue is less numerous, larger in size, and exhibits localized aggregation.

[0119] Comparative Example 5

[0120] It is basically the same as Example 2, except that the primary annealing temperature in the finished product annealing is increased to 500°C.

[0121]

[0122] Comparative Example 6

[0123] It is basically the same as Example 2, except that the primary annealing temperature in the finished product annealing is increased to 450°C.

[0124]

[0125]

[0126] Comparative Example 7

[0127] It is basically the same as Example 2, except that the secondary annealing temperature in the finished product annealing is increased to 350°C.

[0128]

[0129] Comparative Example 8

[0130] It is basically the same as Example 2, except that the secondary annealing temperature in the finished product annealing is reduced to 280°C.

[0131]

[0132] Comparative Example 9

[0133] The process is basically the same as in Example 2, except that the annealing process of the finished product is replaced as follows: the disc is placed in an annealing furnace and heated to the first-stage annealing temperature of 450°C at a heating rate of 600°C / h, held for 1 hour, then cooled to the second-stage annealing temperature of 400°C at a cooling rate of 230°C / h, held for 3 hours, and then cooled to the third-stage annealing temperature of 320°C at a cooling rate of 230°C / h, held for 3 hours, and the annealing is then completed.

[0134]

[0135] As can be seen from the above embodiments and comparative examples,

[0136] Compared with Examples 1 and 2, which employed multi-stage finished product annealing, Comparative Examples 2, 3, and 4, which employed single-stage finished product annealing with different processes, showed significantly lower yield strength, tensile strength, elongation, and plastic strain ratio than Example 2. Furthermore, the performance differences in different directions were substantial, and the uniformity and stability were significantly worse than in Example 2. The quantity, size, and uniformity of the second phase were also significantly inferior to those in Example 2. The examples and comparative examples illustrate that multi-stage finished product annealing can significantly improve the mechanical properties and plastic deformation capacity of 3003 cast-rolled aluminum plates.

[0137] 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 of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A multi-stage annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner pots, characterized in that, include: After holding the 3003 aluminum alloy cold-rolled slab at a first-stage annealing temperature of 460~480℃, it is then held at a second-stage annealing temperature of 300~340℃. The holding time for the first-stage annealing temperature is 0.5~2h; the holding time for the second-stage annealing temperature is 2~6h; the first-stage annealing temperature is denoted as T1 (°C); the second-stage annealing temperature is denoted as T2 (°C); and the thickness of the 3003 aluminum alloy cold-rolled slab is denoted as H (mm). The heating rate of the 3003 aluminum alloy cold-rolled slab to the first-stage annealing temperature is: ℃ / h; The cooling rate from the primary annealing temperature to the secondary annealing temperature is: ℃ / h; The thickness of the 3003 aluminum alloy cold-rolled slab is 1~2.5mm.

2. The multi-stage finished product annealing method for cast-rolled 3003 aluminum alloy used in rice cooker inner pots according to claim 1, characterized in that, include: The 3003 aluminum alloy cold-rolled slab is obtained by cold rolling a cast and rolled 3003 aluminum alloy slab to the specified thickness; the cold rolling includes: the deformation amount of each pass is 10% to 20% of the current thickness.

3. The multi-stage annealing method for the inner pot of a rice cooker made of cast-rolled 3003 aluminum alloy according to claim 2, characterized in that, Intermediate annealing is not performed in the cold rolling process.

4. The multi-stage finished product annealing method for the inner pot of a rice cooker made of cast-rolled 3003 aluminum alloy according to any one of claims 1 to 3, characterized in that, The cold-rolled slab of cast-rolled 3003 aluminum alloy is held at the first-stage annealing temperature, then held at the second-stage annealing temperature, and then cooled to obtain the finished cast-rolled 3003 aluminum alloy for rice cooker inner pot; the cooling includes air cooling.

5. The finished product of cast-rolled 3003 aluminum alloy for rice cooker inner pot, obtained by the multi-stage finished product annealing method of cast-rolled 3003 aluminum alloy as described in any one of claims 1 to 3.

6. The finished product of cast-rolled 3003 aluminum alloy for rice cooker inner pot according to claim 5, characterized in that, The inner pot of the rice cooker is made of cast-rolled 3003 aluminum alloy with a yield strength ≥45MPa, tensile strength ≥115MPa, elongation ≥35%, and plastic strain ratio ≥0.

65.

7. The application of the cast-rolled 3003 aluminum alloy finished product of claim 5 or 6 in the inner pot of a rice cooker.

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