CN110369498B - Method for preparing bulk fine-grained material by flexible rolling - Google Patents

Abstract

The invention discloses a method for preparing a block fine-grained material by flexible rolling, which comprises the following steps: 1) heating the plate blank, and flexibly rolling the plate blank in the length direction, wherein the distance between the rollers is gradually and uniformly reduced in the rolling process, and the deformation of the plate blank is gradually increased; 2) carrying out vertical roll rolling on the width direction of the plate blank, and returning the width of the plate blank to the original size after the vertical roll rolling; 3) rotating the plane of the plate blank by 180 degrees, and repeating the steps 1) and 2), wherein the steps 1), 2) and 3) are a cycle; 4) repeating the steps 1), 2) and 3) for a plurality of times. The geometric shape of the plate blank prepared by the process is unchanged, the uniform deformation is controlled by utilizing the non-uniform deformation, the deformation of different cycle times is completed according to the strain quantity required by the plate blank, the fine crystal material is obtained, and the plate blank with the required specification is finally obtained.

Description

Method for preparing bulk fine-grained material by flexible rolling

technical field

The invention belongs to the field of material plastic processing, in particular to a method for preparing bulk fine-grained material by flexible rolling.

Background technique

The wide application of materials depends on their excellent properties. After the grains of metal materials are refined to a certain extent, they have excellent mechanical properties. Grain refinement strengthening is one of the important methods to improve the properties of metal materials. A large number of experiments have proved that SeverePlastic Deformation (SPD) has a strong ability to refine grains, making the grains reach the nanometer scale. Mature SPD technologies include: Equal Channel Angular Pressing (ECAP), High Compression Torsion (HPT), Cyclic Extrusion or Reciprocal Extrusion and Compression, CEC), high extrusion ratio extrusion (High RatioExtrusion), accumulative rolling (Accumulative Roll Bonding, ARB), continuous variable cross-section recycling extrusion (continuous variable cross-section recycled extrusion, CVCE) and so on.

The various large plastic deformation methods currently researched and developed each have their own advantages and disadvantages. In order to make the large plastic deformation technology more widely used, researching a method for preparing large bulk fine-grained materials by flexible rolling has the advantages of improving material properties and expanding the scope of application. important technical and economic significance.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a method for preparing bulk fine-grained material by flexible rolling, which can accumulate strain amount, refine grains, improve plastic deformation ability, and can realize the preparation process of large-scale fine-grained material for industrial production.

To achieve the above object, the technical scheme adopted in the present invention is:

A method for preparing bulk fine-grained material by flexible rolling, comprising the following steps:

1) The slab is heated, and the length of the slab is flexibly rolled, and the distance between the rolls is gradually and uniformly reduced during the rolling process;

2) Vertical roll rolling in the width direction of the slab;

3) Rotate the slab plane by 180°, repeat steps 1), 2), and step 1), 2), and 3) are one cycle;

4) Repeat steps 1), 2), and 3) several times.

Further, in step 1), the maximum strain amount e=ln(B ₀ /B), and the range of e is 0.69-0.92, wherein: B ₀ is the original slab thickness, and B is the minimum slab thickness after rolling.

Further, in step 2), the vertical rolling deformation rate ε _L =ΔL/L ₀ , the range of ε _L is 20-30%, wherein: ΔL is the vertical rolling amount in the long direction, and L ₀ is the vertical rolling amount. Length of slab before rolling.

Further, the slab is made of magnesium alloy or aluminum alloy.

Further, the slab temperature is 250°C-350°C, and the roll temperature is 180°C-230°C.

Further, the slab temperature is 300°C-350°C.

Further, when the slab temperature is lower than the lower temperature limit, the slab is heated to perform temperature compensation.

Further, the roller surface is coated with lubricant.

Further, the slab is made of AZ31 magnesium alloy, and the length, width and height are respectively 80mm, 50mm and 40mm.

Further, 1) heating the slab to 350°C, and flexibly rolling the slab in the longitudinal direction. During the deformation process, the distance between the rolls gradually decreases uniformly, and the deformation of the slab gradually increases, and the maximum strain amount e=ln(B ₀ /B)=0.80;

2) Vertical roll rolling is carried out on the width direction of the slab, and the slab width is returned to the original size after the vertical roll is deformed, and the relative rolling amount of the vertical roll ε _L =△L/L ₀ =27%;

3) Rotate the slab horizontally by 180° and repeat steps 1) and 2).

The beneficial effects of the present invention are as follows:

1. The method of the present invention realizes flexible rolling by controlling the distance of the rolls, and controls the uniform deformation of the rolling;

2. The method of the present invention controls uniform deformation through uneven deformation, so that the amount of strain is accumulated, and large-scale magnesium alloy and aluminum alloy slabs can be effectively refined;

3. The method of the present invention can keep the slab geometry unchanged, and can provide large-scale slabs with excellent performance, which is beneficial to the wide application of magnesium alloys and aluminum alloys;

4. The method of the present invention has the advantages of small anisotropy and good shape of the rolled slab, a larger cumulative strain amount can be obtained, and the effect of microstructure refinement is obvious;

5. The method of the present invention can significantly refine grains and improve the properties of magnesium alloys, aluminum alloy sheets and other alloys.

Description of drawings

The accompanying drawings forming a part of the present application are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the attached image:

Fig. 1 is the working schematic diagram of the method of the present invention for longitudinal rolling;

Fig. 2 is the working schematic diagram of vertical roll rolling of the method of the present invention;

Fig. 3 is the flow chart of the method of the present invention;

Figure 4 shows the original microstructure of the AZ31 magnesium alloy slab and the microstructure after different cyclic deformation.

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with the embodiments. It should be noted that the embodiments in the present application and the features of the embodiments may be combined with each other in the case of no conflict.

The following detailed descriptions are all exemplary descriptions and are intended to provide further detailed descriptions of the present invention. Unless otherwise specified, all technical terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present invention.

The process for preparing fine-grained material by flexible rolling of the present invention, its implementation steps are:

As shown in Figure 1, 1) send the slab into the rolling mill along the length direction for flexible rolling, the roll spacing gradually decreases evenly during the deformation process, and the slab deformation gradually increases;

As shown in Figure 2, 2) Roll the slab in the width direction with vertical rolls, and return to the original size after the vertical rolls are deformed by rolling;

3) Rotate the slab plane by 180°, repeat steps 1) and 2) to complete a cycle of deformation;

As shown in Figure 3, 4) Repeat the process of flexible rolling and vertical roll rolling, that is, repeat steps 1), 2), and 3) several times, and use the uneven deformation to control the uniform deformation, the amount of strain is accumulated, and the grains are gradually refined , and finally rolled into sheets of required specifications.

The present invention uses the true strain variable to calculate the amount of deformation each time, and its formula is as follows:

Maximum strain e=ln(B ₀ /B), where B ₀ is the thickness of the original slab, and B is the minimum thickness of the slab after rolling;

After rolling and extending twice, the deformation is uniform, and the strain is the same, and the cumulative strain is multiplied by the number of cycles n.

In the present invention, in order to make the flexible rolling deformation proceed smoothly, the temperature of the magnesium alloy slab is between 250°C and 350°C, preferably between 300°C and 350°C, the rolls are preheated to between 180°C and 230°C, and the deformation During the process, the slab temperature will drop, and when the temperature is lower than the lower limit, it should be heated for temperature compensation.

The slab of the invention is deformed by flexible rolling. During rolling, an appropriate lubricant must be used to evenly spread it on the surface of the roll to prevent sticking to the roll and affect the surface quality of the plate.

In the present invention, according to the practice of rolling 20-40mm magnesium alloy slabs by the current production rolling mill, each time the true strain e is about 0.69-0.92. If the method of the present invention is used to deform the AZ31 magnesium alloy slab, the cumulative strain per cycle is e=ln(B ₀ /B)=0.80, and the vertical rolling ratio ε _L =ΔL/L ₀ =27%. After two cycles of deformation, the average grain size was refined from 25.4 μm to 7.9 μm. The fine grains grew slightly in the second cycle, but the grain size distribution was more uniform. After three cycles, part of the coarse grains were refined, and the average grain size was 5.2 μm.

Example 1:

As shown in Figure 4, a slab processed from standard AZ31 magnesium alloy was used to prepare the sample, with a grain diameter of about 25.4 μm and a geometric size of 40×50×80 (B×H×L). First, the magnesium alloy slab was heated. At 350° C., rolling is performed along its length direction, and the slab is a wedge-shaped plate after rolling, and the maximum strain amount e=ln(B ₀ /B)=0.80.

In the second step, the rolled slab is subjected to widthwise vertical roll rolling, the relative rolling amount of each vertical roll is ε _L =ΔL/L ₀ =27%, and the vertical roll returns to the original shape and size after vertical roll rolling.

The magnesium alloy slab was rotated horizontally by 180°, and the first two steps were repeated. After two cycles of deformation, the grains were refined to 7.9 μm, and after three cycles, the grains grew slightly, with an average size of 5.2 μm.

It is known from the technical common sense that the present invention can be realized by other embodiments without departing from its spirit or essential characteristics. Accordingly, the above-disclosed embodiments are, in all respects, illustrative and not exclusive. All changes within the scope of the present invention or within the scope equivalent to the present invention are encompassed by the present invention.

Claims (10)

1. A method for preparing a blocky fine-grained material by flexible rolling is characterized by comprising the following steps:

1) heating the plate blank, and flexibly rolling the plate blank in the length direction, wherein the distance between the rollers is gradually and uniformly reduced in the rolling process;

2) carrying out vertical roll rolling on the width direction of the plate blank;

3) rotating the plane of the plate blank by 180 degrees, and repeating the steps 1) and 2), wherein the steps 1), 2) and 3) are a cycle;

4) repeating the steps 1), 2) and 3) for a plurality of times.

2. The method according to claim 1, wherein in step 1), the maximum strain e ═ ln (B)₀B), e ranges from 0.69 to 0.92, wherein: b is₀The thickness of the original slab is B, and the minimum thickness of the rolled slab is B.

3. The method of claim 1, wherein in step 2), the vertical rolling deformation rate_L＝△L/L₀，_LIn the range of 20-30%, wherein △ L is the rolling amount of the long vertical roll, L₀The length of the plate blank before vertical rolling.

4. The method of claim 1, wherein the slab is a magnesium alloy or an aluminum alloy.

5. The method of claim 1, wherein the slab temperature is 250 ℃ to 350 ℃ and the roll temperature is 180 ℃ to 230 ℃.

6. The method of claim 1, wherein the slab temperature is from 300 ℃ to 350 ℃.

7. The method of claim 5 or 6, wherein the hot slab is temperature compensated when the slab temperature is below a lower temperature limit.

8. The method of claim 1, wherein the roll surfaces are coated with a lubricant.

9. The method according to claim 1, wherein the slab is AZ31 magnesium alloy material with length, width and height of 80mm, 50mm and 40mm respectively.

10. The method of claim 9,

in the step 1), the slab is heated to 350 ℃, the slab is flexibly rolled in the length direction, the roller distance is gradually and uniformly reduced in the deformation process, the deformation of the slab is gradually increased, and the maximum strain e is ln (B)₀/B)＝0.80；

In the step 2), the slab is rolled by the vertical rolls in the width direction, the width of the slab returns to the original size after the rolling deformation of the vertical rolls, and the relative rolling quantity of the vertical rolls_L＝△L/L₀＝27％。

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