CN1199747C - Amorphous alloy precision parts superplastic drop-forging shaper and method thereof - Google Patents

Abstract

The present invention relates to a superplastic die forging forming device and a method thereof for amorphous alloy precision parts. The device is composed of a vacuum furnace (1), a changeable press head and a die, wherein the changeable press head is composed of an inner press head (2), an outer press head (3), a slide block (4) and a connecting seat (5); the die is composed of a die (7) and an ejecting mechanism (8). The technology of the present invention is implemented in the way that a blank and the die are put in the vacuum furnace and are started to be heated when the vacuum degree reaches 8*10#+<-3>Pa; the heating speed is from 0.5 DEG C/s to 3.0 DEG C /s; the heating temperature is from Tg to Tx; the range of forming strain rate is from 1*10#+<-2> to 5*10#+<-4>s#+<-1>. The present invention has the advantages that the present invention is suitable for forming bulk amorphous alloy material with high supercooling regions, such as a Zr-series, a La-series, a Pd-series, etc.; the dimensional precision of the prepared part is from (+/-) 0.1% to (+/-) 0.3%; the surface roughness Ra is less than 0.8 mu m, and even can reach the mirror surface in the nanometer level.

Description

Apparatus and method for superplastic die forging forming of amorphous alloy precision parts

Technical field:

The invention belongs to the technical field of forming new amorphous alloy materials, and in particular provides a superplastic die forging forming device and method for amorphous alloy precision parts. It can be used in the forming of bulk amorphous alloys with large supercooled regions such as Zr-based, La-based, and Pd-based alloys.

technical background:

Precision forming technology is a very important part of advanced manufacturing technology. It is the key technology of many national defense and civilian cutting-edge products. It has a major impact on improving a country's industrial competitiveness and national defense security [Li Minxian et al. Frontiers of Precision Forming Technology Development. China Machinery Engineering, 2000, 11(1-2): 183-186]. Fine parts, especially parts with three-dimensional complex shapes, can be prepared by precision casting, precision plastic forming or injection molding. Generally speaking, the minimum hole diameter and wall thickness that can be formed by precision casting are greater than 2mm, and the size and surface accuracy of the formed parts are low; injection molding has advantages in the manufacture of small parts with complex shapes (size less than 50mm, weight less than 250g) , but the surface roughness of 1-1.6 μm and the dimensional accuracy of ±0.3% that can be achieved at the highest level of precision still cannot meet the requirements of some special precision devices, and the stability of size and process is difficult to accurately control[ Cao Yongjia. Opportunities and Challenges for the Development of Metal Injection Molding. Powder Metallurgy Industry, 2001, 11(3): 7-17]; Precision Plastic Forming, whether using ordinary materials or superplastic materials (currently, fine Crystalline superplastic materials), cannot overcome the unfavorable factors such as low product surface precision and abnormal tool wear caused by the anisotropy of grains and the influence of grain boundaries in the deformation process. At the same time, for some parts, such as straight teeth The precision forming of cylindrical gears is a mature technology that can be used in industrial production and needs to be further developed and perfected.

The preparation of bulk amorphous alloys is one of the important achievements in the field of material research in recent years, but it has not been widely used as structural materials. Bulk amorphous alloys have high strength (the tensile strength of Zr-based and Pd-based bulk amorphous alloys exceeds 1600MPa), excellent corrosion resistance (the corrosion resistance of Ni-based bulk amorphous alloys is 100 times that of stainless steel above), high impact fracture energy (the impact fracture energy of Zr-based and Pd-based bulk amorphous alloys reaches 63kJ/mm ² and 70kJ/mm ² respectively, while the impact fracture energy of aluminum-based high-strength alloys is 12-36kJ/mm2 mm ² ) and low thermal expansion coefficient, high hardness, etc. [Inoue A, Hashimoto K. Amorphous and Nanocrystalline Materials. Tokyo: Springer, 2001]. Therefore, using bulk amorphous alloys to prepare precision parts can obtain better performance than conventional structural materials.

Bulk amorphous alloys are in a Newtonian viscous fluid state with a strain rate sensitivity index m=1 in the supercooled region (that is, between the glass transition temperature and the crystallization start temperature) (even if a small amount of crystallization occurs, the strain rate in the supercooled region The sensitivity index is also far greater than the requirements of general superplastic materials m≥0.3), which is an ideal superplastic material. And its lower processing temperature makes it more advantageous in the selection of mold materials, reducing thermal shock to the mold and saving energy.

On the other hand, there are few researches on superplastic forming of fine parts in China, and there are no related research reports on superplastic forming of bulk amorphous alloys.

Therefore, using bulk amorphous alloys as forming materials to conduct research on superplastic forming of precision parts and prepare fine parts with excellent performance, high dimensional accuracy and surface accuracy will further expand the use of bulk amorphous alloy materials and superplastic forming. The scope of application of plastic forming technology.

Invention content:

The object of the present invention is to provide a device for superplastic die forging forming of large amorphous alloy precision parts and a process for preparing large amorphous alloy precision parts by using the device. It can form a variety of complex shape parts with an outer diameter of 0.1-100mm and a thickness of 0.1-50mm, such as gears, solid or hollow stepped shafts (taper shafts) and equiaxed flat and thin parts. According to the use requirements, complexity and size range of different parts, Zr-based, La-based, Pd-based, Cu-based bulk amorphous alloys with large supercooled regions can be selected as forming materials. The dimensional accuracy of the prepared parts is between ±0.1% and ±0.3%, and the surface roughness Ra is less than 0.8 μm, which can even reach nanoscale mirror surface.

The device of the present invention consists of three parts: a vacuum furnace 1, a replaceable pressure head and a mould. The replaceable indenter is composed of an inner indenter 2, an outer indenter 3, a slider 4 and a connecting seat 5, and the mold is composed of a mold 7 and an ejection mechanism 8. The ultimate vacuum degree of the vacuum furnace is 3×10 ^-3 Pa. It adopts resistance heating method and the maximum temperature is 800°C. It can be filled with nitrogen or argon to form a protective atmosphere. The indenter part can be replaced. For the forming of solid parts, remove the outer indenter 3, slider 4, and coupling seat 5, and replace the inner indenter 2 with an integral flat indenter to achieve one-time forming; for hollow parts, use The combined indenter mechanism shown in 1 realizes two-step forming: that is, the blank 6 and the mold 7 are heated to a predetermined temperature in a vacuum furnace; Synchronously move downwards to fill the cavity with the billet, and complete the first step of forming—filling; then the slider 4 slides into the coupling seat 5, the outer pressure head 3 is connected to the coupling seat 5, and the inner pressure head 2 continues downward alone Movement, forming the inner hole, and completing the second step of forming - punching. The main feature of the forming process of hollow parts is that the two actions of filling and punching are completed continuously in the vacuum furnace. The part of the mold 7 is equipped with an ejection mechanism 8, and after the forming is completed and unloaded, the parts are directly ejected from the cavity of the mold 7.

For hollow parts, in order to improve the dimensional accuracy of the product, according to the shape of the part and the size of the blank, the secondary forming method (refer to the specific embodiment) can also be used, that is, firstly, the integral flat pressing head is used for preliminary filling and forming to improve the shape of the blank. The similarity to the shape of the cavity, and then replace it with a combined indenter for forming.

The precision parts superplastic forming process of the present invention is: according to the use requirements of different parts, respectively select Zr-system, La-system, Pd-system or Cu-system bulk non- For crystal alloy blanks, place the blanks and molds in a vacuum furnace. When the vacuum reaches 8×10 ^-3 Pa, start heating at a heating rate of 0.5-3.0°C/s; the heating temperature should be between Tg and Tx (Tg and Tx is the glass transition temperature and crystallization start temperature of the selected alloy, respectively) to ensure forming in a superplastic state; the forming strain rate ranges from 5×10 ^-4 to 1×10 ^-2 s ^-1 .

The main advantages of the present invention are: the use of vacuum or protective atmosphere ensures the surface quality of formed parts; the use of ejection mechanism and special pressure head mechanism ensures continuous completion of forming and demoulding in a vacuum furnace, reducing the process flow and process turnaround time. A two-step forming process is adopted for hollow parts, which reduces the forming pressure and improves the effect of filling the cavity. The selection of bulk amorphous alloy materials with lower superplastic forming temperature and excellent performance reduces the requirements for mold materials and forming equipment. The formed parts have clear contours, stable and precise dimensions, and their mechanical properties are much better than those of conventional structural materials (such as stainless steel, titanium alloy, medium and low carbon steel, etc.).

Description of drawings

Fig. 1 is a schematic diagram of the superplastic die forging forming device of the present invention. It consists of a vacuum furnace 1, an inner pressure head 2, an outer pressure head 3, a slider 4, a connecting seat 5, a blank 6, a mold 7, and an ejection mechanism 8.

Fig. 2 is a diagram of gear parts formed by the device of the present invention. Meshing parameters: tooth profile angle: α=20°, number of teeth: z=24, modulus: m=0.25

Detailed ways:

The forming object is a spur gear with a hub as shown in Figure 2, which is used in an instrument. The hub wall thickness is 1mm, the inner hole diameter is φ2.6mm, the dimensional tolerance is 0～+0.01mm, and the surface roughness is 1.6μm; The diameter of the top circle is φ6.5mm, the dimensional tolerance is -0.02～0mm, and the roughness of the tooth surface is 1.6μm. The part is required to have high strength, high wear resistance and high corrosion resistance. To this end, a Zr _41.25 Ti _3.75 Cu _{12 5} Ni ₁₀ Be _22.5 bulk amorphous alloy rod with a diameter of φ5mm was used as the forming material (the compression yield strength at room temperature was greater than 1.9GPa, and the Vickers hardness was greater than 5.0GPa) for superplastic forming. The forming temperature is 380-395°C, and the strain rate is 1×10 ^-3 ～5×10 ^-4 s ^-1 . The forming process is carried out in two steps: the first step is to use the integral flat punch to make the metal initially fill the tooth shape and the hub part, and at the same time form part of the inner hole; the second step is to use the combined piercing punch to form the inner hole and force the metal to form a diameter direction flow to further fill the tooth profile and the lower corner of the hub. The formed gear has been tested and analyzed to confirm that there is no crystallization phenomenon, and the original excellent performance of the bulk amorphous alloy blank is better maintained. At the same time, the dimensional accuracy and surface roughness of the formed part meet the design requirements.

Claims (5)

1, a kind of precision parts made of non-crystalline alloy superplastic die forging building mortion is characterized in that: be made up of vacuum drying oven (1), replaceable pressure head, mould three parts; Replaceable pressure head is made up of inner ram (2), outer ram (3), slide block (4), coupling seat (5), and mould is made up of mould (7), ejecting mechanism (8); The final vacuum of vacuum drying oven is 3 * 10 ^-3Pa adopts the resistance heated mode, 800 ℃ of maximum temperatures, but inflated with nitrogen or argon gas form protective atmosphere; The pressure head part can be changed; Be shaped after the end unloading, directly part ejected in the die cavity of mould (7).

2, a kind of according to the described superplastic die forging building mortion of claim 1, it is characterized in that: to solid part forming, remove outer ram (3), slide block (4), coupling seat (5), inner ram (2) is replaced by monoblock type concora crush head, realize once-forming.

3, a kind of according to the described superplasticity cross-forge of claim 1 building mortion, it is characterized in that: to the shaping of hollow parts, then adopt the combination pressure heads mechanism to realize the shaping of two steps: promptly blank (6) and mould (7) are heated to predetermined temperature in vacuum drying oven; Under the stressed outside effect, inner ram (2) and outer ram (3) move downward synchronously by the effect of slide block (4), make blank filling die cavity, finish the first step and are shaped---fill type; Slide block (4) slips in the coupling seat (5) then, outer ram (3) connects with coupling seat (5), and inner ram (2) continues separately to move downward, the shaping endoporus, finishing for second step is shaped---punching, realize the hollow parts forming process fill type and twice action of punching finished in vacuum drying oven continuously.

4, a kind of according to the described superplastic die forging building mortion of claim 1, it is characterized in that: for hollow parts, also can adopt the secondary forming method, promptly at first adopting monoblock type concora crush head to carry out preliminary filling is shaped, improve the similitude of blank shape and die cavity shape, be replaced by the combined type pressure head then and form.

5, a kind of method with the described superplastic die forging device of claim 1 shaping precision parts made of non-crystalline alloy, it is characterized in that: with Zr-system, La-system, Pd-system or Cu-Al-Cu-Zn block amorphous alloy is the shaping blank, blank and mould are placed vacuum drying oven, when vacuum reaches 8 * 10 ^-3During Pa, begin heating, 0.5～3.0 ℃/s of firing rate; Heating-up temperature should be between Tg～Tx, and glass transformation temperature and crystallization that Tg and Tx are respectively selected alloy begin temperature, is shaped under the superplasticity state guaranteeing; Shaping strain rate scope is 5 * 10 ^-4～1 * 10 ^-2s ^-1

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