A method for preparing large-size uniform ultra-fine grain thin disc components by using swing roller die forming

Abstract

The present application relates to the technical field of metal material processing, in particular to a method for preparing large-size uniform ultra-fine-grain thin disc components by swing rolling die forming, which realizes grain size refinement by implementing different pass swing rolling die forming deformation on circular plate to obtain different strain accumulation effects. The swing rolling die forming using staggered tooth die structure and the mixed track movement form of the die have the advantages that the upper die is locally contacted with the blank during the forming process, and has the characteristics of continuous local loading forming, the maximum axial load after forming is only 1 / 8 of the overall loading of the conventional die forging die, the effect of limiting die pressing accumulation of large plastic deformation can be realized under smaller tonnage equipment, the strain accumulation is as high as 9 or more, the strain uniformity is good, the standard deviation is 0.510, and the forming quality is good.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of metal material processing, and particularly relates to a method for preparing large-size uniform ultra-fine-grain thin disc components by adopting swing rolling die forming. BACKGROUND

[0002] With the rapid development of aerospace, transportation and military equipment fields, the preparation of materials with high specific strength and good plasticity matching, the realization of product lightweight and the reduction of energy consumption have become the research focus in the international material field. Refining grains can effectively improve the comprehensive mechanical properties of metal materials. Compared with traditional materials, ultra-fine-grain materials exhibit more superior mechanical properties, forming properties, and physical and chemical properties, and have a very broad application prospect.

[0003] Large plastic deformation is an advanced plastic forming process method developed in the late 1970s. It can introduce as much large strain as possible to refine grains while ensuring that the shape and size of the material remain unchanged. In addition, it can be used to prepare ultra-fine-grain materials with excellent performance. Traditional large plastic deformation processes such as high-pressure torsion, equal channel angular pressing, and multi-axial forging still have defects such as non-uniform material structure, low production efficiency, high cost, and complex process route, and are mostly used for forming small-size block materials. Only the cumulative roll bonding and repeated bending-straightening processes are suitable for the preparation of sheet materials. However, the cumulative roll bonding process has strict process conditions, and the repeated bending-straightening process has the disadvantage of insufficient deformation effect, which greatly limits its application in the preparation of large-size ultra-fine-grain metal sheets.

[0004] Constrained groove pressing (CGP) is a new type of large plastic deformation method, which has obvious advantages in preparing large-size ultra-fine-grain metal sheets. This method uses a set of bending and flattening dies to repeatedly apply pure shear deformation to the sample, which can accumulate a large amount of shear strain in the material without changing the original size and shape of the sample. Compared with other processes, the constrained groove pressing process not only overcomes the shortcomings of equal channel angular pressing, high-pressure torsion and multi-axial forging in preparing large-size ultra-fine-grain sheets, but also avoids the strict requirements for the surface quality of the sheet and the rolling roller and the environmental atmosphere in the process of cumulative roll bonding. Unlike the repeated bending-straightening process, the constrained groove pressing process applies pure shear deformation to the sheet, which is easier to accumulate sufficient equivalent plastic strain. In addition, its process is relatively simple, and the equipment requirements are low, which has a good industrial application prospect. However, most of the current research objects are limited to metals or alloys with good plasticity, while there are few studies on magnesium alloys and titanium alloys, which have great industrial application potential but poor room temperature plasticity. In addition, there is a technical bottleneck of insufficient equipment tonnage in the large plastic deformation of difficult-to-deform materials to prepare ultra-fine-grain components.

[0005] The cumulative strain effect of the conventional plastic deformation method is unsatisfactory and the process is complicated, and the equipment is difficult to meet the further development of the new process, which seriously limits the development and application of large-size ultra-fine grain plate.

[0006] In view of the above defects, the inventor has finally obtained the present application after long-term research and practice. SUMMARY

[0007] The present application aims to solve the problems of the cumulative strain effect of the conventional plastic deformation method being unsatisfactory and the process being complicated, and the equipment being difficult to meet the further development of the new process, and provides a method for preparing large-size uniform ultra-fine grain thin disc components by using swing rolling die forming.

[0008] In order to achieve the above-mentioned purpose, the present application discloses a method for preparing large-size uniform ultra-fine grain thin disc components by using swing rolling die forming, comprising the following steps:

[0009] S1, placing a circular blank to be processed into a first pair of rolling bending dies for first-stage rolling bending;

[0010] S2, using a rolling flattening die to flatten the rolled blank in the first stage;

[0011] S3, using a second pair of staggered-tooth rolling bending dies to roll the blank flattened in the first stage in the second stage;

[0012] S4, using a rolling flattening die consistent in shape and size with the foregoing S2 to flatten the blank completed in the second stage of rolling, and the entire blank produces uniform deformation after the above-mentioned two-stage swing rolling die forming process;

[0013] S5, repeating the above one-pass steps S1-S4 to increase the cumulative effective deformation, so as to obtain ultra-fine grain thin disc components without changing the size of the plate blank.

[0014] The die used in the swing rolling die forming includes two pairs of rolling bending dies and one pair of rolling flattening dies, each pair of rolling bending dies includes an upper die and a lower die, and the wave peaks and wave troughs of the upper die and the lower die are engaged with each other.

[0015] The steps S1-S5 are all carried out at a constant temperature, and the heating temperature T is the warm forming temperature of the blank material.

[0016] Before the step S1, finite element numerical analysis is carried out on the swing rolling die forming process by using finite element software to determine the swing rolling process parameters.

[0017] The swing rolling process parameters are: the swing angle of the upper die is 4°, the upward feeding speed of the lower die is 1mm / s, the movement trajectory of the upper die is circular, the directions of rotation and revolution are opposite, and the rotation speed is 6r / s.

[0018] The crest and trough opening angle of the upper die and the lower die is 58.4°.

[0019] The swing-rolling process parameters of the first stage rolling in the step S2 and the second stage rolling in the step S4 are same as the swing-rolling process parameters of the first stage rolling in the step S1.

[0020] The swing-rolling process parameters of the second stage rolling in the step S3 are as follows: the swing angle of the upper die is 4°, the upward feeding speed of the lower die is 1mm / s, the movement track of the upper die is a rose curve shape, and the rotating speeds of the inner and outer eccentric sleeves are 12r / s and -14r / s respectively.

[0021] Compared with the prior art, the present application has the beneficial effects that: the present application combines the swing-rolling process with the limited die pressing process, designs a swing-rolling die pressing die, utilizes the characteristics that the die and the blank are locally contacted in the swing-rolling process, and achieves the effect of accumulating large plastic deformation of the limited die pressing process under the action of smaller load. Thus, the technical bottleneck of insufficient equipment tonnage faced by the preparation of super-fine grain components from difficult-to-deform materials is broken through, and large-size high-performance super-fine grain disc components are prepared at low cost and with labor saving.

[0022] In the aspect of the die structure, the present application introduces a tooth structure on the traditional swing-rolling die, and develops a new swing-rolling die pressing die. The die has two sets of rolling dies and one set of rolling dies. The upper die of the rolling die is still in the shape of a cone, but the tooth structure is introduced on the cone generatrix part of the upper die of the traditional swing-rolling die. Meanwhile, the lower die also increases the tooth structure which is fully engaged with the upper die to ensure the uniformity of deformation. The tooth structures of the two sets of rolling dies are distributed in a staggered manner, and the rolling die is consistent with the traditional swing-rolling die. Secondly, in the aspect of the forming process, the circular track and rose curve track movement modes are introduced in the rolling and rolling stages respectively to solve the quality problems such as incomplete filling. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 It is a deformation schematic diagram of the swing-rolling die pressing process of the present application;

[0024] Figure 2 It is a staggered distribution schematic diagram of the two sets of rolling dies of the present application;

[0025] Figure 3 It is a structure schematic diagram of the first set of rolling dies of the present application;

[0026] Figure 4 It is a structure schematic diagram of the second set of rolling dies of the present application;

[0027] Figure 5 It is a structure schematic diagram of the rolling die of the present application;

[0028] Figure 6is the load time evolution curve of stage 1;

[0029] Figure 7 This is the load time evolution curve of stage 1 using the conventional compression method;

[0030] Figure 8 To simulate the equivalent strain change cloud diagram of the second-pass blank plastic deformation;

[0031] Figure 9 This is a bar chart showing the equivalent strain changes of the blank during the second pass plastic deformation simulation. DETAILED DESCRIPTION

[0032] The above and other technical features and advantages of the present invention are described in more detail below with reference to the accompanying drawings.

[0033] This embodiment provides a method for preparing large-sized uniform ultrafine-grained thin disk-like components by using swing-rolling die pressing. After completing the blanking and basic processing of the blank, the blank is first placed in a first pair of bending dies for initial bending, so that the blank is formed into a preset bending shape; then the prefabricated blank is placed in a flattening die for flattening treatment; and the same bending-flattening treatment is performed again using a second pair of bending dies with staggered teeth and a flattening die.

[0034] The method for preparing ultrafine-grained thin disk parts using Ti6Al4V with a size of Φ38×2mm as raw material is carried out in accordance with the following process steps:

[0035] S1, place the round blank to be processed into Figure 3 The first stage of bending is performed in the first pair of bending molds shown in FIG. Figure 1 As shown in (a) and (b);

[0036] S2, use Figure 5 The flattening die shown in the figure performs the first stage of flattening on the bent blank. Figure 1 As shown in (c);

[0037] S3, use Figure 4 The second pair of bending dies shown in the figure performs the second bending of the blank after being flattened in the first stage. Figure 1 As shown in (d) and (e) in the figure. Since the two pairs of rolling dies have staggered teeth, the crests and troughs are staggered alternately, as shown in Figure 2 As shown, the overall strain is more uniform.

[0038] S4, use Figure 5 The second stage flattening is performed on the blank that has completed the second stage of bending by a flattening die having the same shape and size as shown in the figure. Figure 1(f) shown in the figure. After the two stages of the swing roll die forming process, the entire blank produces uniform deformation. The two stages of the swing roll die forming process are referred to as the first pass of the swing roll die.

[0039] S5, repeating the above steps S1-S4, completing the second pass of the swing roll die forming.

[0040] The blank heating temperature is 920°C, and the deformation process is carried out at a constant temperature.

[0041] In step S1, the swing roll process parameters are: the upper die swing angle is 4°, the lower die upward feeding speed is 1 mm / s, the upper die motion trajectory is a circular shape, the rotation and revolution directions are opposite, and the rotation speed is 6 r / s.

[0042] In steps S1 and S3, the opening angle α of the wave crest and the wave trough of the upper and lower dies determines the deformation amount under the same process parameter conditions. If the opening angle is too large, the cumulative strain in a single pass is small; if the opening angle is too small, folding defects are easily produced in the flattening stage. Considering the deformation amount and forming quality, the opening angle is determined to be 58.4°.

[0043] In steps S2 and S4, the swing roll process parameters are the same as those in step S1.

[0044] In step S3, the swing roll process parameters are: the upper die swing angle is 4°, the lower die upward feeding speed is 1 mm / s, the upper die motion trajectory is a rose line shape, and the inner and outer eccentric sleeve rotation speeds are 12 r / s and -14 r / s, respectively.

[0045] Within one pass, the first stage of bending is defined as stage 1, the first stage of flattening is defined as stage 2, the second stage of bending and flattening are defined as stage 3 and stage 4, respectively.

[0046] The load-time evolution curve of the first stage stage 1 is as shown in Figure 6 The load-time evolution curve of the first stage using conventional die forging, i.e., direct pressing, is as shown in Figure 7 It can be seen that the maximum axial load using the swing roll die forming method is greatly reduced compared to the conventional die pressing method, which is about 1 / 8 of the conventional die pressing method, only 1.72 t.

[0047] The strain simulation diagrams of the two passes are as shown in Figure 8 and Figure 9 After two passes of accumulation, it can be seen that the total cumulative average strain of two passes is as high as 9.01, the strain at the wave trough is relatively large, there is a certain strain partition, but the overall uniformity is good, and the standard deviation is 0.510.

[0048] With the accumulation of passes, the deformation amount is larger and larger, and the large plastic deformation of the required structure can be realized, and the comprehensive use performance is significantly improved. The specific deformation pass can be determined according to actual needs.

[0049] The above only describes the preferred embodiments of the present application, which are only illustrative but not restrictive. It is understood by those skilled in the art that many changes, modifications and even equivalents can be made to the present application within the spirit and scope defined by the claims of the present application, but all will fall within the protection scope of the present application.

Claims

1. A method for preparing large-sized uniform ultrafine-grained thin disk components by using swing die pressing, characterized in that: The following steps are involved: S1, placing the circular blank to be processed into the first bending die for the first stage of bending; S2, using a flattening die to flatten the bent blank in the first stage; S3, using a second pair of staggered tooth bending dies to bend the blank after the first stage of flattening in the second stage; S4, using a flattening die having the same shape and size as in S2 to flatten the blank after the second stage of bending, the entire blank is uniformly deformed after the above two stages of pendulum-rolling deformation process; S5, repeating the above steps S1 to S4 to increase the accumulation of effective deformation, thereby obtaining an ultrafine-grained thin disk without changing the outer dimensions of the slab; The dies used in the swing die pressing process include two pairs of bending dies and one pair of flattening dies. Each pair of bending dies includes an upper die and a lower die. The wave crests and wave troughs of the upper die and the lower die engage with each other.

2. The method for preparing large-sized uniform ultrafine-grained thin disk components by using swing die pressing as claimed in claim 1, characterized in that: The steps S1 to S5 are all performed at a constant temperature, and the heating temperature T is the warm forming temperature of the blank material.

3. The method for preparing large-sized uniform ultrafine-grained thin disk components by using swing die pressing as claimed in claim 1, characterized in that: Before step S1, finite element software is used to perform finite element numerical analysis on the oscillating die pressing process to determine the oscillating process parameters.

4. The method for preparing large-sized uniform ultrafine-grained thin disk components by using oscillating die pressing as claimed in claim 3, characterized in that: The swing rolling process parameters are: upper die swing angle 4°, lower die upward feed speed 1 mm / s, upper die motion trajectory is circular, rotation and revolution directions are opposite, and rotation speed is 6 r / s.

5. The method for preparing large-sized uniform ultrafine-grained thin disk components by using oscillating die pressing as claimed in claim 1, characterized in that: The opening angle of the wave crest and the wave trough of the upper die and the lower die is 58.4°.

6. The method for preparing large-sized uniform ultrafine-grained thin disk components by using swing die pressing as claimed in claim 1, characterized in that: The swing rolling process parameters for the first stage of flattening in step S2 and the second stage of flattening in step S4 are the same as the swing rolling process parameters for the first stage of bending in step S1.

7. The method for preparing large-sized uniform ultrafine-grained thin disk components by using swing die pressing as claimed in claim 1, characterized in that: The swing rolling process parameters of the second stage of bending in step S3 are: upper die swing angle 4°, lower die upward feed speed 1 mm / s, upper die motion trajectory is a rose line shape, and inner and outer eccentric sleeve rotation speeds are 12 rpm and -14 rpm respectively.

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