METHOD FOR PRODUCING COLD-STORAGE MATERIAL FOR EXTREMELY LOW TEMPERATURE

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PROBLEM TO BE SOLVED : To provide a method for producing a cold-storage material for extremely low temperatures, excellent in mechanical properties to mechanical vibration, filling pressure and the like. SOLUTION : A magnetic cold-storage material granular aggregate 1 satisfying the following conditions (a) to (c) is prepared. Then 1 g of magnetic cold-storage material granule is extracted from the magnetic cold-storage material granular aggregate, and the rate of granules which are destroyed when compressive force of 5 MPa is applied to the aggregate by a compression tester is measured. Subsequently the magnetic cold-storage material granular aggregate, whose rate of granules destroyed when compressive force of 5 MPa is applied thereto is ≤1 wt.%, is sorted. The condition (a) : ≥70 wt.% of magnetic cold-storage material granule constituting the magnetic cold-storage material granular aggregate has the ratio of long diameter to short diameter of 5 or less. The condition (b) : ≥70 wt.% of magnetic cold-storage material granule constituting the magnetic cold-storage material granular aggregate has a granule diameter in the range of 0.01-3.0 mm. The condition (c) : the granular aggregate 1 comprises an intermetallic compound including a rare-earth element represented by RMz (R is a predetermined rare-earth element; M is a predetermined metallic element; and z is a number within the range of 0.001-9.0) or ARh (A is a predetermined rare-earth element). COPYRIGHT : (C)2013, JPO&INPIT