JP3616591B2 - Crystal grain refinement method and grain refiner for metal material - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method and a crystal grain refining apparatus for improving various properties such as strength and toughness by refining metal or alloy crystal grains.
[0002]
[Prior art]
When crystal grains of a metal or alloy (hereinafter collectively referred to as a metal material) are refined, properties such as strength and toughness are improved. Refinement of crystal grains is also effective in canceling the anisotropy of the metal material. However, since there is a limit to the refinement of crystal grains by conventional thermomechanical processing, refinement of crystal grains due to strain introduced by strong processing has been studied.
As a method for refining crystal grains by strong processing, there are a compression twisting method, an ECAP method (Equal Channel Angular Pressing), a repeated rolling joining method and the like (Light Metal Forum Vol. 5 (1999), pages 32 to 40). In the compression torsion method, a cylindrical metal sample is loaded into a cylindrical container, and a strong strain is introduced into the metal sample by applying a compressive force and a twisting force to one end of the metal sample using a punch. Is miniaturized. In the ECAP method, a rod-shaped metal sample is pushed through a metal mold having an L-shaped hole, and the crystal grain is refined by subjecting the metal sample to high strain processing without changing the cross-sectional shape. In the repeated rolling joining method, a plate-shaped metal sample is rolled, folded, and then crystal grains are refined by strong strain introduced by repeating rolling again.
[0003]
[Problems to be solved by the invention]
The ECAP method is mainly used for crystal grain refinement of an aluminum alloy, but it is difficult in principle to increase the size of the apparatus. In the repeated rolling joining method, in order to form a good joint and reduce the rolling load, it is necessary to perform rolling again in a warm region below the recrystallization temperature. On the other hand, the compression twist method can refine crystal grains to submicron or several microns with a relatively simple operation. However, in the conventional compression torsion method, the crystal grains in a thin material or a narrow region on one side in the thickness direction are often miniaturized, and it is difficult to refine the crystal grain in a thick material or a wide region.
[0004]
[Means for Solving the Problems]
The present invention has been devised to solve such problems, and by adopting a container that can be rotated independently from the upper and lower punches, a twist in the reverse direction is added to the metal material loaded in the container, The object is to refine crystal grains in a wide area even with a relatively thick metal material, or to refine crystal grains simultaneously with solidification molding of metal powder.
[0005]
In order to achieve the object of the grain refinement method of the present invention, the container loaded with the metal material can be rotated independently from the upper punch and the lower punch, and the upper punch and / or the metal material can be rotated while pressed against the metal material. By rotating the lower punch relatively torsionally , the metal material is repeatedly subjected to compression torsion .
[0006]
The crystal grain refining device includes a container loaded with a metal material to be subjected to compression twisting, and an upper punch and a lower punch pressed against both ends of the metal material loaded in the container. By twisting and rotating the upper punch and / or the lower punch relative to each other in a state where the container is disposed independently of the upper punch and the lower punch, the twist deformation necessary for crystal grain refinement is applied to both ends of the metal material. Added repeatedly .
[0007]
[Action]
The crystal grain refining apparatus according to the present invention makes a container 1 loaded with a metal material (sample) S independent of upper and lower punches 2 and 3 as shown schematically in FIG. It is possible. For the metal material (sample) S, a solid metal material or metal powder is used. With solid metal materials, crystal grains can be refined without changing the shape, and with metal powders, crystal grains can be refined simultaneously with solidification.
[0008]
When the upper punch 2 and the lower punch 3 are pressed against the metal material (sample) S loaded in the container 1 with the reduction force F and the upper punch 2 is twisted, the container 1 is rotated in the same direction as the upper punch 2 by the friction force, and the twist The lower punch 3 to which no is added rotates relative to the container 1 in the opposite direction. As a result, the torsional deformation in the upside down direction is applied to the metal material (sample) S by the punches 2 and 3.
The twist deformation is also applied to the metal material (sample) S by twisting the lower punch 3 instead of the upper punch 2 or twisting and rotating the punches 2 and 3 in the opposite directions. In any case, since the twisting force T is applied from both ends of the metal material (sample) S, plastic strain necessary for crystal grain refinement is introduced even if the metal material is thick.
[0009]
On the other hand, in the conventional compression torsion method (FIG. 2), the punch 2 is pressed against the metal material (sample) S loaded in the recessed portion of the fixed container 1 so that the metal material (sample) S is deformed. Only a twisting force T is applied to one end of the. Therefore, the effect of the twisting force T applied to the metal material (sample) S is significantly less than that of the method of the present invention, and the metal material (sample) S on the bottom surface side of the recess of the container 1 is sufficient for crystal grain refinement. Plastic strain is not introduced.
[0010]
As is clear from this comparison, the compression torsion method of the present invention applies a twisting force T to both ends of the metal material (sample) S, so that the plastic strain twice as much as that of the conventional method can be obtained by simple calculation. It can be introduced into the material (sample) S, and the crystal grains are efficiently miniaturized. Even in the case of a relatively thick metal material (sample) S, crystal grains are refined over a wide region by the twisting force T applied from both ends.
[0011]
[Example 1]
As the metal material (sample) S, a pure Al ingot having a diameter of 25 mm and a height of 10 mm was used. This pure Al ingot material had an average crystal grain size of around 100 μm. A metal material (sample) S is loaded in the container 1 and heated to 300 ° C., a punching force F of 75 MPa is applied by the punches 2 and 3, a twist angle ± 45 degrees, a twist frequency 1/6 Hz, and the number of twists 50 times. Then, plastic strain was introduced into the metal material (sample) S by twisting the upper punch 2.
[0012]
When the metal material (sample) S after processing was observed, the crystal grains were refined to an average particle diameter of 1 to 5 μm in a region of 2 to 3 mm from the punches 2 and 3 side. Further, since plastic strain is also introduced in the vicinity of the inner peripheral surface of the container 1, the crystal grains are miniaturized.
On the other hand, in the conventional method (FIG. 2) in which the metal material (sample) S loaded in the fixed container 1 is twisted, the punch 2 is twisted under the same conditions. However, the refinement of the crystal grains only progressed, and the initial average grain size remained at 100 μm in other parts including the bottom surface of the concave portion of the container 1.
[0013]
[Example 2]
A green compact obtained by compacting Bi-Te-Sb alloy powder having an average particle size of 70 μm into a cylindrical shape having a diameter of 25 mm and a height of 10 mm at room temperature was used as the metal material (sample) S. The green compact S was loaded into the container 1 and heated to 500 ° C., and the punches 2 and 3 were pressed against the metal material (sample) S with a rolling force F75 MPa. Then, plastic strain was introduced into the green compact S under the conditions of a twist angle of ± 45 degrees, a twist frequency of 1/6 Hz, and a twist frequency of 10 times.
[0014]
When the green compact S after processing was taken out from the container 1 and observed, the powder was sufficiently solidified and formed into an integral cylindrical sample. The crystal grain size of the sample sampled from each part in the height direction and radial direction of the obtained compact was measured. As a result, it was refined to an average particle diameter of 1 to 5 μm in the region of 2 to 3 mm from the punch 2 and 3 side, and the refinement was particularly remarkable in the vicinity of the inner peripheral surface of the container 1.
By changing the holding temperature, the twist frequency, and the number of twists, the miniaturization region also changed, and it was possible to miniaturize almost the entire region of a sample having a maximum height of 10 mm.
[0015]
【The invention's effect】
As described above, in the present invention, twisting deformation is applied to both ends of the metal material by making the container independent from the upper and lower punches, so that the plastic strain necessary for crystal grain refinement is the conventional compression twisting method. Compared to, it is introduced in a wide area. Therefore, even if it is a thick metal material, crystal grain refinement is possible in a wide range, and the characteristics of the metal material can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic view of a crystal grain refining apparatus according to the present invention. FIG. 2 is a diagram for explaining a conventional compression twisting method.

Claims (2)

The container loaded with the metal material can be rotated independently of the upper punch and the lower punch, and the upper punch and / or the lower punch is relatively twisted and rotated while being pressed against the metal material. A method for refining crystal grains of a metal material, characterized by repeatedly loading A container loaded with a metal material to be compression-twisted, and an upper punch and a lower punch pressed against both ends of the metal material loaded in the container, the container being rotated independently of the upper punch and the lower punch A crystal grain refining device that is freely arranged and repeatedly applies twist deformation to both ends of a metal material by relative twist rotation of an upper punch and / or a lower punch.

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