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A Forming Method for Nano/Ultrafine Crystal Cylindrical Parts Prepared by Small Strain

A technology of ultra-fine grain and cylindrical parts, which is applied in the field of plastic forming of metal materials, can solve the problems of difficult control of forming quality, small volume of bulk materials, large deformation, etc., and achieves favorable control of forming quality and mechanical properties Uniform, good plastic effect

Active Publication Date: 2017-06-06
SOUTH CHINA UNIV OF TECH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

However, the volume of the bulk material prepared by this method is small, and the plastic strain required is large. During the processing, it needs to go through repeated severe plastic deformation, the process is complicated, and it needs to be processed into the required parts later. Due to its processing difficulty, Seriously restricts the application of nano / ultrafine grain parts
[0004] In order to solve the problem of preparing large-scale nano / ultrafine-grained parts, there are currently two main methods. One is to repeatedly plastically deform the surface of the processed part to form a surface nano / ultra-fine-grained layer, but this method is only to realize The nano / ultrafine crystallization of the surface of the part is guaranteed, and the grain size of the internal structure is still micron; Ultra-fine crystal cylindrical parts, this method can realize the overall refinement of grains, so that the average grain size can reach 600nm, but this method requires a large amount of deformation (thinning rate needs to reach 87%)
[0005] For the actual parts, on the one hand, it is necessary to obtain the overall refined grains to achieve the overall strengthening and toughness of the parts, and at the same time, it is hoped that the degree of plastic deformation will not be too large to facilitate industrial production. For strong spinning, When its thinning rate reaches about 90%, its forming quality is difficult to control

Method used

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  • A Forming Method for Nano/Ultrafine Crystal Cylindrical Parts Prepared by Small Strain

Examples

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Embodiment 1

[0038] Seamless cylindrical blank, the material is 10 steel (0.1% carbon content), the shape is as figure 1 Shown, its inner diameter d=182mm, wall thickness δ=2.4mm, length l=500mm. In addition to size requirements, it is also necessary to obtain an ultra-fine grain structure with an average grain size of less than 1 μm.

[0039] 1. Use 10-steel seamless steel pipe with a specification of φ194*6mm available on the market as the blank, with an inner diameter of 182mm and a wall thickness of 6mm (such as Figure 4 As shown), the wall thickness of the parts required for forming pipes of this specification is reduced from 6mm to 2.4mm, and the thinning rate is 60%. Therefore, the tube blank is used for multi-pass staggered spinning after quenching, and finally recrystallization annealing. The microstructure and Figure 7 Closely, the average grain size is 40 μm.

[0040] Lengthen the blank by 15mm as the fixed part of the bottom, take 10mm as the trimming allowance at the mou...

Embodiment 2

[0047] Seamless cylindrical blank, the material is 20 steel (0.2% carbon content), the shape is as figure 1 Shown, its inner diameter d=68mm, wall thickness δ=1.8mm, length l=200mm. In addition to size requirements, it is also necessary to obtain an ultra-fine grain structure with an average grain size of less than 1 μm.

[0048] 1. The 20-steel seamless steel pipe with a specification of φ76*4mm that can be purchased on the market is used as the blank, with an inner diameter of 68mm and a wall thickness of 4mm (such as Figure 4 Shown), using the parts required for blank forming of this specification, the wall thickness is reduced from 4mm to 1.8mm, and the thinning rate is 55%. Therefore, the part is to be prepared by quenching, staggered spinning, and recrystallization annealing (such as Figure 6 shown). The microstructure of this steel pipe blank is as follows Figure 7 As shown, the average grain size is about 50 μm.

[0049] Lengthen the blank by 15mm as the fixed ...

Embodiment 3

[0055] Seamless cylindrical blank, the material is 20 steel (0.2% carbon content), the shape is as figure 1 Shown, its inner diameter d=100mm, wall thickness δ=1mm, length l=200mm. In addition to size requirements, it is also necessary to obtain an ultra-fine grain structure with an average grain size of less than 1 μm.

[0056] 1. The wall thickness of the seamless steel pipe with an inner diameter of 100mm that can be purchased on the market is at least 4mm. Since the thinning rate cannot exceed 60% during strong spinning of the blank, otherwise cracks will occur, and the nano / Ultra-fine crystal cylindrical parts have good plasticity and can be used for subsequent spinning forming. Therefore, tube blanks with a specification of φ108*4mm are used. After quenching, staggered spinning is performed, and the wall thickness is reduced from 4mm to 2mm (reduced Thinness rate 50%), followed by recrystallization annealing, its plasticity recovery, and then staggered spinning, its wa...

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Abstract

The invention discloses a forming method for preparing nanometer / ultrafine drain cylindrical parts with small strain. The forming method comprises the following steps: (1) seamless cylindrical blanks are prefabricated according to the wall thicknesses and the lengths of metal cylindrical parts and according to a material volume invariable principle; (2) the seamless cylindrical blanks are quenched to obtain lath martensite tissues; and a quenching medium adopts 5% of NaCl solution; (3) the quenched seamless cylindrical blanks are mounted on a main shaft of a spinning machine for multiple times of staggered spinning formation, so that the wall thickness thinning rate of the seamless cylindrical blanks reaches 50-60%; and (4) the seamless cylindrical blanks obtained in the step (3) are put in a heating furnace with a temperature of 450-500 DEG C for heating to reach a recrystallizing temperature for keeping about 0.5 h, and then are cooled by water. The forming method can obtain the cylindrical parts having whole nanometer / ultrathin grain structures under the condition of smaller deformation, has no need of acute plastic deformation, and facilitates to control the forming quality.

Description

technical field [0001] The invention relates to the field of plastic forming of metal materials, in particular to a forming method for preparing nanometer / ultrafine crystal cylindrical parts with small strain. Background technique [0002] Nanomaterials refer to solid materials with a grain size of nanometer scale (1-100nm); ultrafine-grained materials refer to solid materials with a grain size of 100-1000nm. Nano / ultrafine-grained materials have excellent comprehensive mechanical properties due to their fine grains, and have become a research hotspot in the field of materials and equipment manufacturing. [0003] At present, there are many methods for preparing nanomaterials by severe plastic deformation, such as equal channel angular extrusion, cumulative stack rolling, multi-directional forging, high-pressure torsion, etc. However, the volume of the bulk material prepared by this method is small, and the plastic strain required is large. During the processing, it needs t...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): B21D22/16C21D1/18C21D7/00
CPCB21D22/16C21D1/18C21D7/00
Inventor 肖刚锋夏琴香程秀全徐腾
Owner SOUTH CHINA UNIV OF TECH
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