Production process of thin-wall deep-cavity multi-rib aluminum alloy main machine shell

Abstract

The invention belongs to the field of aluminum alloy processing, and particularly relates to a thin-wall deep-cavity multi-rib aluminum alloy host shell production process which comprises the following steps: homogenizing a cast aluminum bar, and cutting the homogenized cast aluminum bar into a blank; symmetrically-distributed axial grooves are machined in the periphery of the blank, and sawtooth-shaped sharp edges are formed; the finished blank is subjected to cold and hot pretreatment of first heating, liquid nitrogen edge cold treatment and reheating; feeding the pretreated blank into a special forging and pressing die for forging and pressing; and finally, a finished product is obtained through quenching, aging, finish machining and anodic oxidation. According to the method, the blank is subjected to surface finishing and special cold and hot pretreatment before forging, so that the problems that the thin-wall deep-cavity multi-rib structure is uneven in side wall thickness and poor in perpendicularity during forging are effectively solved, the quality of an anodic oxide film in a corner angle area is remarkably improved, a film layer is prevented from losing efficacy in advance, and the service life of the film layer is prolonged. And meanwhile, unique mould pressing precipitation lines are formed on the surface of the product and can be used as anti-counterfeiting marks.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of aluminum alloy processing, and particularly relates to a production process of a thin-wall deep-cavity multi-rib aluminum alloy main machine shell. BACKGROUND

[0002] At present, the computer main machine shell is mainly produced by an extrusion+CNC+welding process. After casting aluminum rods are subjected to homogenization, heating, peeling, extrusion, correction, cutting, quenching, aging and CNC processes, the rods are processed into qualified products. The production process has many procedures, a long cycle, high cost and low material utilization.

[0003] For a product with a deep cavity, thin side wall and large deformation, the side wall thickness is not uniform and the side wall is not perpendicular in the forging and pressing process.

[0004] Since the aluminum alloy main machine shell is a thin-wall deep-cavity multi-rib structure, the following phenomena are prone to occur during forging and pressing:

[0005] 1. After forging and pressing, the die pressing separation lines existing on the surface of the product are large in area. After subsequent anodic oxidation, the product is not beautiful enough, the metal texture is not enough, and the product is seriously homogenized with other similar products on the market; the product cannot reflect its uniqueness.

[0006] 2. For the thin-wall deep-cavity multi-rib aluminum alloy main machine shell, due to the use of the forging and pressing process, uneven forging and pressing is prone to occur at the corner area. After anodic oxidation is performed again at the corner area, the anodic oxidation film at the corner area is prone to have defects such as foaming spots, powdering, cracking, uneven film and brittleness. The other flat or curved areas of the main machine shell product generally do not have these defects. The above defects can easily lead to premature failure of the anodic oxidation film.

[0007] Based on this, the present application is proposed. SUMMARY

[0008] The purpose of the present application is to provide a production process of a thin-wall deep-cavity multi-rib aluminum alloy main machine shell to solve the above problems.

[0009] A production process of a thin-wall deep-cavity multi-rib aluminum alloy main machine shell, comprising the following steps:

[0010] Step 1, heat the casting aluminum rod for homogenization, and cool it to room temperature after homogenization is completed;

[0011] Step 2, cut the homogenized aluminum rod into a blank, process symmetrical distributed axial grooves on the outer periphery of the blank along the axial direction of the blank, and set a spacing area between the adjacent two axial grooves. The axial grooves are arc grooves. After processing is completed, a surface-finished blank is obtained, and a regular sharp edge similar to a sawtooth is formed on the surface of the blank;

[0012] Step 3, the surface finished blank is preheated, cooled by liquid nitrogen on the edge, and then reheated for cold and hot pretreatment;

[0013] Step 4, the cold and hot pretreated blank is sent into a special forging die for forging forming to obtain a forged blank;

[0014] Step 5, the forged blank is sequentially quenched, aged, finished and modified, and anodized to obtain the thin-walled deep-cavity multi-rib aluminum alloy main shell.

[0015] Further improvement, in step 2, the width-depth ratio of the axial groove is the ratio of the maximum groove width of the axial groove to the maximum groove depth of the axial groove, and the width-depth ratio of the axial groove is 1.6-1.7; the ratio of the maximum groove width of the axial groove to the width of the interval is 3, and the width of the interval is 1-1.4mm.

[0016] Further improvement, in step 3, the cold and hot pretreatment process includes three stages:

[0017] First stage: preheat the surface finished blank;

[0018] Second stage: pour a ring of liquid nitrogen on the edge of the preheated blank, and after pouring the liquid nitrogen, the blank is cooled at room temperature;

[0019] Third stage: reheat the blank treated in the second stage;

[0020] Further improvement, in step 1, the average temperature is 450-500℃, and the holding time is 4-6h.

[0021] Further improvement, in the first stage, the preheating temperature is 120-125℃, and the holding time is 1-1.5h.

[0022] Further improvement, in the second stage, the ratio of the area of the annular zone formed by pouring liquid nitrogen to the cross-sectional area of the blank without surface finishing is not more than 10%; after pouring the liquid nitrogen, the blank is cooled at room temperature for more than 5h for cooling.

[0023] Further improvement, in the third stage, the temperature is kept at 410-430℃ for 1-1.5h.

[0024] Further improvement, the special forging die includes an upper die and a lower die, and a lateral guide plate and a guide column are arranged between the upper die and the lower die.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. For the deep cavity, thin side wall and large deformation of the product, a special forging die is designed to increase the side wall guide mechanism to ensure the thickness and perpendicularity of the side wall.

[0027] 2. High production efficiency, fewer forming processes, and higher material utilization rate. Forging and pressing can better utilize materials and reduce waste generation; the overall production cycle is shorter, enabling faster mass production.

[0028] 3. The product has good performance. The forging and pressing process causes plastic deformation of the material, resulting in a denser internal structure, higher material strength, hardness, and toughness, and a longer service life for the parts.

[0029] 4. The molded exudate patterns on the surface of the semi-finished main unit casing are small-area patterns with random shapes and relatively uniform distribution, which are highly distinctive. The semi-finished main unit casing is sold separately as a bare part, and the above-mentioned molded exudate patterns can serve as a unique anti-counterfeiting mark.

[0030] 5. By processing a large number of regular sharp edges similar to serrations on the surface of the billet before forging, and then performing cold and hot pretreatment, the processing defects that occur in the corner areas of thin-walled, deep-cavity, multi-rib products can be solved. After subsequent anodizing, the anodized film in the corner areas is less likely to fail prematurely, which significantly improves product quality. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the structure of the special forging die described in this invention;

[0032] Figure 2 This is a schematic diagram illustrating the processing of the surface-trimmed blank according to the present invention;

[0033] Figure 3 This is a side view photograph of the semi-finished main unit casing product described in this invention;

[0034] Figure 4 This is a top view photograph of the semi-finished main unit casing product described in this invention; Detailed Implementation

[0035] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings.

[0036] In the description of this invention, it should be noted that, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," "outer," "front end," "rear end," "head," "tail," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0037] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0038] Example 1

[0039] The thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing manufacturing process of this invention is suitable for main unit casings with a side wall thickness of 1.5mm, a cavity depth of 80mm, and six evenly distributed reinforcing ribs. It uses 6061 cast aluminum rods as raw materials. The specific production steps are as follows:

[0040] Homogenization treatment: Place the 6061 cast aluminum rod into a homogenizing furnace, heat it to 480℃, hold it for 5 hours, and then cool it to room temperature with the furnace to eliminate internal segregation.

[0041] Surface finishing: Based on the forming dimensions of the main unit casing, the homogenized aluminum rod is sawn into blanks with a length of 120mm, and the sawing tolerance is controlled within ±0.5mm; A CNC machining center is used to machine symmetrically distributed axial grooves 51 along the axial direction of the blank 50 on its outer periphery, with a gap 52 between adjacent axial grooves 51. The axial grooves 51 are arc-shaped grooves, with a maximum groove depth of z and a maximum groove width of y. Preferably, the width-to-depth ratio is y / z = 1.7; In this embodiment, since the diameter of the blank 50 is 150mm, if... Figure 2 As shown; therefore, y is preferably 3.6 mm, z = 2.1 mm; x = 1.2 mm; x is the width of the interval 52. After processing, a surface-trimmed blank is obtained, with regular, serrated, sharp edges formed on its surface.

[0042] Hot and cold pretreatment:

[0043] First stage: Place the surface-trimmed billet into a heating furnace for preheating, raise the temperature to 125℃, and hold for 1 hour;

[0044] Second stage: Take the preheated billet out of the heating furnace and pour a ring of liquid nitrogen around the edge of the preheated billet. The ratio of the area of ​​the ring formed by the liquid nitrogen pouring to the cross-sectional area of ​​the unfinished billet 50 is no more than 10%. After the liquid nitrogen pouring is completed, the billet is placed at room temperature for more than 5 hours.

[0045] Third stage: After that, the billet that has been treated in the second stage is put into the heating furnace, heated to 420℃, and held for 1.5 hours to ensure the plastic state of the billet;

[0046] Forging and forming: The forging and forming tonnage is determined to be 800T and the holding time is 10s through simulation. The billet that has undergone the third stage of processing is quickly placed into the lower mold cavity of the special forging die. The main top cylinder of the forging press applies 800T pressure to push the upper die down. After holding the pressure for 10s, the pressure is released to obtain the forged billet.

[0047] Among them, special forging dies such as Figure 1 As shown, the die includes an upper die 10 and a lower die 20, with a side guide plate 40 and a guide post 30 disposed between the upper die 10 and the lower die 20. During the forging process, the guide post 30 and the side guide plate 40 of the special forging die work together to counteract the lateral force and ensure the forming accuracy of the forged blank.

[0048] Quenching treatment: Quickly remove the forged blank and quench it by water quenching at a temperature of 400℃. Cool it to room temperature in no more than 10 seconds.

[0049] Aging treatment: The quenched forging blank is placed in an aging furnace, heated to 140℃, held for 7 hours, and then cooled to room temperature with the furnace to eliminate internal stress.

[0050] CNC finishing: The mounting and mating surfaces of the blank are finished using a CNC machining center, with machining tolerances controlled within ±0.05mm, resulting in a semi-finished main unit casing. Figure 3 , 4 As shown. From Figure 3 and Figure 4 As can be seen, the surface of the semi-finished main unit casing has many small areas of varying colors and random shapes (defined as molding precipitation patterns). The formation mechanism is that the flow of aluminum alloy metal causes changes in grain orientation; areas with different grain orientations often exhibit different gloss levels, and their grain boundaries also differ under a microscope. Because of the presence of these molding precipitation patterns, a special oxide film can be formed during subsequent anodizing.

[0051] Anodizing: Immerse the semi-finished main unit casing in degreasing solution at 60℃ for 12 minutes to remove surface oil, then rinse three times with deionized water; immerse in alkaline washing solution (6% sodium hydroxide solution) at 45℃ for 4 minutes to remove oxide scale and burrs, then rinse thoroughly after neutralization; immerse in acid washing solution (10% phosphoric acid solution) for 1.5 minutes to remove residual oxide film, then rinse thoroughly; finally, using the semi-finished main unit casing as the anode, immerse in an oxidation electrolyte (18% sulfuric acid solution), controlling the voltage at 15V and the current density at 1.5A / dm³. 2The process involves oxidizing at 20℃ for 20 minutes to form an oxide film with a thickness of 10μm; then immersing in an 85℃ sealing solution (boiled and cooled deionized water) for 12 minutes, followed by drying to obtain a qualified main unit casing product. Testing revealed that the sidewall thickness uniformity error was ≤0.02mm, the sidewall verticality error was ≤0.03mm, the tensile strength was 322MPa, and the yield strength was 281MPa. Compared to products of the same specifications produced using existing extrusion + welding processes, the tensile strength increased by 28.0%, the yield strength increased by 33.4%, and the material utilization rate reached 85%. Notably, after sandblasting for 10 minutes at the corners of the main unit casing using rubber wheels, the total area of ​​the detached anodized film was calculated using a scanning method. The anodized film detachment rate is calculated as: total area of ​​detached anodized film / area of ​​the corner area. The sandblasting process involved 200-mesh glass beads as the blasting medium, compressed air pressure of 0.08MPa, a blasting angle of 75°, and a blasting distance of 200mm. In this example, the anodic oxide film shedding rate in the corner area was 1.7%, while the anodic oxide film shedding rate in other planar or curved areas was 0%.

[0052] During testing, it was found that the anodic oxide film at the corners of the main unit casing is prone to defects such as foam spots, powdering, cracks, uneven film, and brittleness, while these defects are generally not present on other flat or curved areas of the main unit casing. The presence of these defects easily leads to premature failure of the anodic oxide film. Therefore, a sandblasting process was used for pre-testing. Anodized oxide films exhibiting these defects showed extensive peeling after sandblasting. However, if there were no defects or other defects (abnormal color, spots, overlapping marks, etc.), even with the sandblasting process of this invention, due to the lower compressed air pressure and shorter processing time, the anodic oxide film generally would not peel off. At most, it would only result in pitted white spots or unevenness on the surface of the anodic oxide film, which would remain attached to the corners of the main unit casing. Therefore, a higher anodic oxide film peeling rate indicates poor quality of the anodic oxide film at the corners of the main unit casing.

[0053] Example 2

[0054] In this example, if the width of the gap is too small, for example, less than or equal to 0.5 mm, it will result in too much concentration of sharp structures and stress. After forging, a large number of tiny pits will appear on the surface. The anodic oxide film near the pits is prone to powdering. After sandblasting, the anodic oxide film peeling rate of other planar or curved areas is greater than 37%.

[0055] If the width of the interval is too large, such as 2mm, it will result in the regular sharp edges being too large. The effect on other planar or curved areas will not be obvious, but for the corner areas where stress is concentrated, the anodic oxide film peeling rate will reach 53.8%.

[0056] Similarly, if the ratio of the maximum width of the axial groove to the width of the interval zone is too large (for example, 4), with a fixed width of the interval zone, the maximum width of the axial groove is too large, which is equivalent to insufficient number of regular sharp edges. During forging, the effect on other planar or curved areas is not obvious, but for the stress-concentrated corner areas, the anodic oxide film peeling rate will reach 41.3%.

[0057] If the ratio of the maximum width of the axial groove to the width of the interval area is too small (e.g., 1.5), it indicates that the distribution of regular sharp edges is too dense. Due to the liquid nitrogen freezing treatment, the subsequent change in the forging flow rate is not as expected, which will lead to a large number of microcracks after forging, resulting in product scrap.

[0058] Therefore, preferably, the width-to-depth ratio of the axial groove is 1.6 to 1.7; the ratio of the maximum groove width of the axial groove to the width of the interval is 3, and the width of the interval is 1 to 1.4 mm.

[0059] Example 3

[0060] In this example, if the ratio of the area of ​​the annular region formed by the liquid nitrogen to the cross-sectional area of ​​the unfinished billet 50 is too large, for example, exceeding 15%, it indicates that the liquid nitrogen has altered the aluminum alloy too much, which will seriously affect the forged product. After forging, a large number of microcracks and cracks will be generated, leading to product scrap.

[0061] Comparative Example 1

[0062] The difference between this example and Example 1 is that the cold and hot pretreatment in this example only involves the third stage, which is to put the billet into a heating furnace, heat it to 420°C, and hold it at that temperature for 1.5 hours to ensure the plastic state of the billet; the rest are the same.

[0063] The molding exudation marks on the product surface were found to be large-area (e.g., generally larger than 3cm). 2 The anodic oxide film peeling rate was 88.3% in the corner areas and 11.5% in other planar or curved areas.

[0064] Comparative Example 2

[0065] The difference between this example and Example 1 is that the cold and hot pretreatment in this example only involves the second and third stages. That is, a ring of liquid nitrogen is poured around the edge of the surface-trimmed billet, and the ratio of the area of ​​the ring formed by the liquid nitrogen pouring to the cross-sectional area of ​​the untrimmed billet 50 is no more than 10%. After the liquid nitrogen pouring is completed, the billet is placed at room temperature for more than 5 hours. Then, the billet that has undergone the second stage treatment is placed in a heating furnace, heated to 420°C, and held for 1.5 hours to ensure the plastic state of the billet. The rest is the same.

[0066] The anodic oxide film peeling rate was 8.6% in the angular areas and 5.7% in other planar or curved areas. This may be because the liquid nitrogen treatment was performed directly without preheating, followed by heating to 420℃, resulting in excessive internal stress. This caused uneven stress release after forging, potentially leading to micro-cracks in other planar or curved areas, thus affecting the subsequent anodizing effect.

[0067] Comparative Example 3

[0068] The difference between this example and Example 1 is that no surface finishing is performed. The sawn blank (with a smooth cylindrical surface) is directly placed in a heating furnace for preheating, heated to 125°C, and held for 1 hour. All other aspects are the same.

[0069] The product surface was found to have large areas of molding precipitation marks, and the anodic oxide film peeling rate in the corner areas was 72.1%.

[0070] In this invention, because regular, sawtooth-like sharp edges are formed on the surface of the billet, and it is first heated, then frozen with liquid nitrogen, and then restored to plasticity at high temperature, it is equivalent to modifying the surface structure of the billet, thereby significantly improving the flow rate of plastic deformation on the surface of the billet. This results in the molding precipitation marks on the surface of the final product being small in area and evenly distributed. At the same time, they are also evenly distributed in the corner areas, which facilitates the subsequent coverage and bonding of the anodized film.

[0071] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A manufacturing process for a thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing, characterized in that, Includes the following steps: Step 1: Heat the cast aluminum rod to homogenize it, and then cool it to room temperature after homogenization. Step 2: Cut the homogenized aluminum rod into blanks, and process symmetrically distributed axial grooves on the outer periphery of the blanks along the axial direction. An interval area is set between two adjacent axial grooves. The axial grooves are arc-shaped grooves. After processing, a blank with a finished surface is obtained, and its surface forms regular sharp edges similar to serrations. Step 3: Perform a cold and hot pretreatment on the surface-trimmed blank by first heating, then cooling the edges with liquid nitrogen, and then heating again. Step 4: The pre-treated billet is fed into a special forging die for forging to obtain a forged billet; Step 5: After quenching, aging, finishing and anodizing the forged blank in sequence, the thin-walled deep cavity multi-ribbed aluminum alloy main body shell is obtained.

2. The manufacturing process for a thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing according to claim 1, characterized in that: In step 2, the width-to-depth ratio of the axial groove is the ratio of the maximum groove width to the maximum groove depth of the axial groove, and the width-to-depth ratio of the axial groove is 1.6~1.7; the ratio of the maximum groove width of the axial groove to the width of the interval area is 3, and the width of the interval area is 1~1.4mm.

3. The manufacturing process for a thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing according to claim 1, characterized in that: In step 3, the cold and hot pretreatment process includes three stages: First stage: Preheat the surface-trimmed blank; Second stage: Pour a ring of liquid nitrogen around the edge of the preheated billet. After pouring the liquid nitrogen, the billet is warmed up at room temperature. The third stage: The billet that has been processed in the second stage is reheated.

4. The manufacturing process for a thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing according to claim 1, characterized in that: In step 1, the average temperature is 450~500℃, and the temperature is maintained for 4~6 hours.

5. The manufacturing process for a thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing according to claim 3, characterized in that: In the first stage, the preheating temperature is 120~125℃, and the temperature is maintained for 1~1.5 hours.

6. The manufacturing process for a thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing according to claim 3, characterized in that: In the second stage, the ratio of the area of ​​the annular region formed by pouring liquid nitrogen to the cross-sectional area of ​​the unfinished billet is no more than 10%; after pouring liquid nitrogen, the billet is placed at room temperature for more than 5 hours for rewarming.

7. The manufacturing process for a thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing according to claim 3, characterized in that: In the third stage, maintain a temperature of 410~430℃ for 1~1.5h.

8. The manufacturing process for a thin-walled, deep-cavity, multi-ribbed aluminum alloy main unit casing according to claim 1, characterized in that: The special forging die includes an upper die and a lower die, with a side guide plate and a guide post provided between the upper die and the lower die.

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