Raw material for shot-peening materials, finished wire, method of manufacturing shot-peening materials, and shot-peening materials

Abstract

The purposes of the present inventions are to provide a raw material for shot-peening materials wherein breaking a wire is prevented in obtaining a finished wire to improve the productivity, to provide a finished wire and a method of manufacturing shot-peening materials by which productivity is improved, and to provide shot-peening materials that are manufactured by that method. The finished wire, of which the area of carbides with a particle size of 2 μm or less is 80% or more of the total area, is manufactured by the steps of wiredrawing a raw material to obtain a wire, and repeatedly annealing and cold-drawing the wire. The raw material for the shot-peening materials comprises, by mass %, 0.95-1.10% carbon, 0.15-0.30% silicon, 0.40% or less manganese, 0.020% or less phosphorus, 0.010% or less sulfur, 1.40-1.60% chromium, 0.0015% or less oxygen, and the remaining materials of iron and unavoidable impurities. The method of manufacturing the shot-peening materials uses that raw material. The shot-peening materials are manufactured by that method.

Description

TECHNICAL FIELD[0001]The present inventions relate to a raw material for shot-peening materials, a finished wire, a method of manufacturing shot-peening materials, and shot-peening materials.BACKGROUND ART[0002]In an existing process of manufacturing shot-peening materials, a raw material, e.g., so-called bearing steel, is wiredrawn to obtain a wire. The wire is cut at the same length as its diameter. The cut wire is then thrown at a rigid wall to round off its edges. The rounded-off wire is ground to a predetermined degree of sphericity. Then, it is quenched and tempered to get a predetermined Vickers hardness. This process is well known (e.g., Japanese Laid-open Publication No. 2001-79766).DISCLOSURE OF INVENTION[0003]However, when a bearing steel that is not modified from a standard steel (e.g., a high carbon chromium bearing steel, SUJ2 of JIS (Japan Industrial Standards) G4805, of which the components are shown in Table 2) has been used as a raw material for shot-peening materi...

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Benefits of technology

[0009]The method of manufacturing the shot-peening materials of the present inventions is characterized in that it comprises the steps of cutting and plastic-forming the finished wire of the second feature to make raw shot-peening materials, and quenching and tempering them. The present inventions provide shot-peening materials that are efficiently manufactured and have a good quality, since they are made from the finished wire, which has a proper elongation and has a reliable quality.

[0010]The tempering parameters are defined by the following equation: T{(21.3 −5.8×[C])+log(t)}: where T denotes the tempering temperature (K), t the tempering time (hr), and [C] the carbon content (%). The tempering temperature T and the carbon content C are selected so that the parameters become 6200-7300. When the tempering temperature T, the carbon content C, and the tempering time t, are selected so that the parameters become 6200-7300, the coarsening of crystalline grains is prevented and the residual stress is relieved, to increase toughness. Thus, that selection is preferable. The method may further comprise the step of plastic-forming the raw shot-peening materials. This method has an advantage in that almost no breaking is generated during a shot-peening process, because the corners of the shot-peening materials are rounded off. Plastic-forming the raw shot-peening material means to make the raw shot-peening material in a spherical shape from a short piece that is made by cutting the finished wire by plastic-forming. That is, the raw shot-peening materials are not rounded by cutting or grinding.

[0011]The method of manufacturing the shot-peening materials of the present inventions is further characterized in that it comprises the steps of wiredrawing a raw material for the shot-peening materials of the first feature to obtain a wire, repeatedly annealing and cold-drawing the wire to obtain a finished wire, obtaining the raw shot-peening materials by cutting the finished wire and plastic-forming, and quenching and tempering the raw shot-peening materials. It has an advantage in that the crystalline grains are refined and the toughness is recovered after the heat treatment.

[0012]The method of manufacturing the shot-peening materials of the present inventions is further characterized in that the quenching temperature is 820-850° C. in the aforementioned method. It has an advantage in that almost no residual austenite is generated, and overall, martensite is uniformly obtained in the structure.

[0013]The shot-peening materials of the present inventions are those manufactured by the methods that are described above

Problems solved by technology

However, when a bearing steel that is not modified from a standard steel (e.g., a high carbon chromium bearing steel, SUJ2 of JIS (Japan Industrial Standards) G4805, of which the components are shown in Table 2) has been used as a raw material for shot-peening materials, there has been a problem of the wire breaking.

This does not improve the productivity of the shot-peening materials.

Thus, the productivity i

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