Mixed powder for powder metallurgy, sintered body, and method of manufacturing sintered body

Abstract

Provided is a mixed powder for powder metallurgy, which, while having a constituent composition that does not contain Ni, a cause of non-uniformity in the metal structure of sintered compacts, and theleading factor behind increased costs of alloy powders, makes it possible to achieve components by sintering compacts of alloyed steel powder, and subsequently subjecting the compacts to carburizing,quenching and tempering, said components having equivalent or superior mechanical properties to components to which Ni has been added. The mixed powder contains a partially diffused alloyed steel powder obtained by diffusion-deposition of Mo on the particle surface of an iron-based powder, in addition to Cu powder and graphite powder. The mixed powder has a constituent composition containing 0.2-1.5 mass% Mo, 0.5-4.0 mass% Cu, and 0.1-1.0 mass% C, with the remainder being made up of Fe and unavoidable impurities, and the partially diffused alloyed steel powder has an average particle diameterof 30-120 [mu]m and a specific surface area of less than 0.10 m2 / g, and the degree of circularity of particles having a diameter of 50-100 [mu]m does not exceed 0.65.

Description

technical field [0001] The present invention relates to a mixed powder for powder metallurgy, in particular to a mixed powder for powder metallurgy suitable for manufacturing high-strength sintered parts for automobiles and a sintered body made using the mixed powder for powder metallurgy. For the mixed powder for powder metallurgy, The density of the sintered body obtained by molding and sintering the alloy steel powder, and the tensile strength and toughness (impact value) after carburizing, quenching and tempering the sintered body are reliably improved. Moreover, this invention relates to the manufacturing method of this sintered compact. Background technique [0002] Powder metallurgy technology can produce parts with complex shapes in a shape very close to the shape of the product (so-called near-net shape) with high dimensional accuracy, so it is a technology that can greatly reduce cutting costs. Therefore, powder metallurgy products are used in various fields as va...

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Problems solved by technology

From the point of view of cost, the addition of several mass % Ni is also extremely unfavorable

In addition, when Ni is used as an alloy element, there is a problem that long-term sintering is required to sufficiently diffuse Ni in iron powder or steel powder.

In addition, when the diffusion of Ni, which is an austenite phase stabilizing element, is insufficient, the Ni-rich region is stabilized as an austenite phase (hereinafter also referred to as γ phase), and the Ni-poor region is excluding this. Phase stabilization other than that, as a result, the metal structure of the sintered body becomes inhomogeneous

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