Analiza postopka oblikovanja za izkovke valjev iz aluminijeve zlitine 2A14
In the trial production process of 2A14 aluminum alloy cylinder forgings, a blank opening process scheme of cross upsetting drawing, horse frame expanding, and core shaft elongation was adopted. Ring rolling production was carried out on a vertical ring rolling machine, and forgings meeting the mechanical performance requirements were produced.
2A14 is a deformable aluminum alloy that can be heat treated and strengthened, belonging to the Al Cu Mg Si system. It has high strength and thermoplastic properties, and is suitable for manufacturing high load parts with thick sections. It is widely used in fields such as aerospace and civil transportation. For the manufacturing of large-sized cylindrical forgings, due to the phenomenon of uneven microstructure, coarse grains, and component segregation in large-diameter bars, conventional forging methods are used for forming, which poses difficulties in forging through and ensuring the quality of forgings. By applying large plastic deformation to the ingot through forging, the microstructure and grain refinement can be improved, thereby improving the comprehensive mechanical properties of the material and obtaining a rolling ring material with excellent microstructure. Then, the rolling ring process can be used to produce forgings that meet the mechanical performance requirements. On the basis of our own deep cylindrical forging ring rolling technology, combined with the inherent process characteristics of aluminum alloy materials, our company has summarized a set of blank opening processes suitable for aluminum alloy cylinder forming. We have used the largest vertical ring rolling machine in China to produce and successfully manufactured 2A14 aluminum alloy cylinder forgings with a size of Φ1020mm×Φ900mm×1270mm.
1. Condition of 2A14 aluminum alloy cylinder forgings
The raw material for the forging is 2A14 ingot provided by Southwest Aluminum Industry Co., Ltd. The chemical composition of the raw material is shown in Table 1. The delivery status is T6 (solid solution+artificial aging). The mechanical performance requirements are shown in Table 2. The dimensions of rough machined odkovki are shown in Figure 1. The forging weight is relatively heavy (cutting weight 1250kg).
2. Analysis of the Forming Process for 2A14 Aluminum Alloy Cylinder Forgings
The traditional manufacturing method for cylinder forgings is to use free forging forming. It is difficult for large-sized bars to achieve a fine and uniform structure, and it is necessary to use sufficient plastic deformation during billet opening to transform the as-cast structure into a uniform and fine structure suitable for subsequent forging processing, thereby improving the comprehensive mechanical properties of the material. Therefore, how to maximize the amount of deformation and refine the microstructure is a key process for the opening of large-sized aluminum alloy cylinder forgings. Research has shown that the large plastic deformation method (SPD) can significantly refine the grain size and greatly improve the strength and toughness of the material. However, this method is currently in the experimental research stage. For the forming of aluminum alloy cylinder parts, Zhang Wenwen et al. studied the blank opening process of large-sized 2219 aluminum alloy using multi-directional forging. The castings were subjected to upsetting and elongation deformation in three directions, and the forming of large-sized ring blanks was achieved through horse frame expanding. In industrial production, the use of cross upsetting and drawing with sufficient deformation can eliminate the directionality of aluminum alloy structure and properties, improve the uniformity of structure and properties, and improve the overall performance of the product. The process is simple and the cost is low.
Table.1 Chemical Composition of Raw Materials (Mass Fraction,%)
Table.2 Mechanical Property Requirements for 2A14 Aluminum Alloy Cylinder Forgings
Figure.1 Dimensional Drawing of Forgings
In the trial production process of 2A14 cylinder forgings, a combination of cross upsetting drawing, horse frame expanding, and mandrel elongation was used to increase the forging ratio and deformation in the three directions of vertical and horizontal height, thereby improving the comprehensive performance of the product. The specific process flow for manufacturing 2A14 cylinder forgings is: cutting → grinding → billet making → machining inner hole → horse frame expanding hole → mandrel elongation → ring rolling → heat treatment → performance testing → mechanical processing. The initial forging temperature of the billet is 470 ℃, and the final forging temperature is controlled above 370 ℃. The billet was produced using a cross upset drawing method on a 36MN hydraulic press, with an overall deformation of 265%. The schematic diagram of billet production is shown in Figure 2. The cross cross upsetting deformation increases the deformation degree of the ingot, ensuring the uniformity of the ingot deformation. During the forging process, the contact surface between the billet and the hammer head and the lower anvil often changes, which will not cause excessive local temperature reduction, thus reducing the risk of cracks on the end face.
After the cross upsetting and drawing of the ring blank, it is cooled and machined with an inner hole. The ring blank is then placed in a heating furnace for heating, and the ring material for rolling the ring is made by expanding the hole on a horse frame (with an overall deformation of 10%) and elongating the core shaft (with an overall deformation of 20%). Then, the material is reheated for the second time and rolled on a 2300mm vertical ring rolling machine. The radial feed rate of the ring rolling machine is (0.6-0.7) mm/s, and the deformation is 49%. The heat treatment adopts T6 (solid solution+artificial aging) treatment, and the specific method is: insulation at 500 ℃ for 4 hours, water cooling; 160 ℃ insulation for 7 hours, air-cooled. Saw a 120mm sample at one end of the cylinder for physical and chemical testing, and then machine it to the required size.
3. Analysis of Trial Production Results of 2A14 Cylinder Forgings
The external dimensions of the cylinder forgings trial produced according to the above process plan meet the processing requirements, and the inspection results meet the requirements of Ultrasonic testing Methods for Wrought Aluminum and Magnesium Alloy Products (GB/T6519-2013). Cut the test material from the ring blank and take samples in three directions: axial, radial, and tangential. The sampling positions are shown in Figure 3. The mechanical performance test results are shown in Tables 3 to 5, and the mechanical properties meet the requirements. The measured hardness value is 130HBW.
(1) The cross upsetting drawing, horse frame expansion, and mandrel elongation process scheme for 2A14 aluminum alloy cylindrical forging has sufficient deformation, which is conducive to refining the structure, improving the mechanical properties of the material in different directions, and obtaining good rolling ring blanks.
Figure.2 Schematic diagram of forging billet
Figure.3 Schematic diagram of sampling location
Table.3 Testing Results of Tangential Mechanical Properties of Forgings
|Sampling Location And Direction||Rm/MPa||Rp0.2/MPa||A(%)|
|Testna vrednost||Vzdolžno 0 °||435||330||13. 5|
|Vzdolžno 90 °||430||330||8. 5|
|Navpično 180 °||420||295||11|
|Navpično 270 °||420||300||10|
Tabela.4 Rezultati preskusov osnih mehanskih lastnosti odkovkov
|Mesto in smer vzorčenja||Rm/MPa||A(%)|
|Standard value||Vodoravno po širini (aksialno)||≥355||4-14|
|Testna vrednost||Osno 0 °||425||11|
|Aksialno 90 °||430||12|
|Aksialno 180 °||415||11.5|
|Aksialno 270 °||415||10|
Tabela.5 Rezultati preverjanja radialnih mehanskih lastnosti odkovkov
|Mesto in smer vzorčenja||Rm/MPa||A(%)|
|Standard value||Vodoravno po debelini (radialno)||≥335||3-14|
|Testna vrednost||Radialno 0 °||385||4|
|Radialno 90 °||390||4|
|Radialno 180 °||365||4.5|
|Radialno 270 °||375||4.5|
(2) Obročni polproizvod po odprtju proizvaja navpični stroj za valjanje obročev z najvišjim tlakom na Kitajskem. Mehanske lastnosti odkovka ustrezajo konstrukcijskim zahtevam. Uporaba tehnologije valjanja obroča lahko reši problem mehanskih lastnosti, ki ne morejo izpolnjevati zahtev, ki jih prinaša tradicionalno prosto kovaški obroč in lahko izpolnijo zahteve letalskih in vesoljskih sestavnih delov glede zmogljivosti strukture obroča, enakomernosti in stabilnosti serije.
Avtor: Liu Zhi