Shots made from zinc-based alloy

Abstract

Shots made from a zinc-based alloy is provided, wherein no risk for explosion caused by powder dusts exists. They achieve a high performance in deflashing and grinding and cleaning by shot blasting and a high ability to create a high compressive residual stress. The lost amounts of them by shooting are small. The shots are made from a zinc-based alloy that contains three components that include A1 of 0.5 to 6.5 mass % and Cu of 0.5 to 4.5 mass % as additional elements, or that contains four components that further include Mg of 0.01 to 0.2 mass % as additional elements, wherein the ratio of the mass of A1 to Cu (A1 / Cu) is 1.0 to 13.0, wherein the total amount of A1 and Cu (A1+Cu) is 1.5 to 10.5 mass %, and wherein the Vickers hardness of the shots is 90 to 190 HV.

Description

TECHNICAL FIELD[0001]The present invention relates to shots that are used for a process by projecting (by blowing) them, such as shot blasting or shot peening. The shot blasting is utilized to remove fins or burrs (below, “deflashing”) in nonferrous metallic parts, such as aluminum die-castings and aluminum castings, to strip sand from castings, to remove burnt deposits of coatings and parting agents, or to remove scales or flow lines (below, “grinding and cleaning”). The shot peening is utilized to improve the fatigue strength of nonferrous metallic parts or welded parts of nonferrous metallic parts.[0002]Herein, the wording “Vickers hardness” means the value measured in accordance with JIS Z 2244 under the condition that the applied force is 0.4093 N and the time for applying the force is 10 to 15 sec. It is expressed as “◯◯◯ HV 0.05,” abbreviated as “◯◯◯ HV.”[0003]The mark “%,” which is used to denote the contents of an alloy, means “mass %,” unless otherwise indicated.BACKGROUND...

AI Technical Summary

Benefits of technology

[0044]Since the shots of the present invention are made from zinc-based alloys, a cloud of dust caused by shots breaking cannot be easily burst and the minimum concentration to burst is high. Thus shots made from zinc-based alloys that are safe can be provided.

[0045]Further, since the shots made from zinc-based alloys have a high hardness (a Vickers hardness of 90 HV or more), the abilities for deflashing and for grinding and cleaning by shot blasting are high, so as to process workpieces over a short period. Thus the productivity is high. Since the shots have a high toughness that cannot be achieved by the conventional shots, the consumption of shots decreases and the amount of dust generated by shots breaking decreases.

[0046]Similarly, for the use for shot peening, the shots of the present invention, which have high hardness and toughness, effectively cause the surface layers of workpieces to plastically deform, to thereby generate a compressive residual stress. Similar to the use for shot blasting, the amount of dust generated by shots breaking decreases.

[0047]For the shots made from zinc-based alloys of the present invention the decrease in the mechanical strength caused by re-crystallization is relatively small, so that the Vickers hardness of the shots is stable during their use. Hence, after shot blasting or shot peening, workpieces are finished with little variation so that the quality of surface treatments is constant.

[0048]By the shots made from zinc-based alloys of the present invention, the dust contains no element that is listed in the PRTR regulations. Further, there is just a small amount of dust. Thus the shots made from zinc-based alloys are preferable in view of environmental preservation and work safety.

Problems solved by technology

Thus the grinding and cleaning abilities are not sufficient.

Because of the characteristics of aluminum, a cloud of dust caused by breakages of the shots during shot blasting can easily burst.

Thus in view of work safety and environmental preservation, their use tends to be restricted.

Dust from shots made from zinc-based alloys cannot easily burst because of the breakages of the shots and because it takes a higher concentration to burst than those made from aluminum-based alloys and stainless steels.

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