Kitz Corporation

Kitz Metalworks Corporation

Tomoyuki Ozasa

Hisanori Terui

Kazuhito Kurose

Hidenobu Tameda

Masaru Yamazaki

Teruhiko Horigome

Yukihiro Hirata

Hideki Kotsuji

Kei Ito

By enhancing a stress corrosion cracking resistance in a leadless brass alloy, specifically by suppressing a velocity of propagation of corrosion cracks in the brass alloy, a straight line crack peculiar to the leadless brass alloy is suppressed, a probability of cracks coming into contact with &#x3b3; phases is heightened and local corrosion on the brass surface is prevented to suppress induction of cracks by the local corrosion, thereby providing a leadless brass alloy contributable to enhancement of the stress corrosion cracking resistance. The present invention is directed to an Sn-containing Bi-based, Sn-containing Bi+Sb-based or Sn-containing Bi+Se+Sb-based leadless brass alloy excellent in stress corrosion cracking resistance, having an &#x3b1;+&#x3b3; structure or &#x3b1;+&#x3b2;+&#x3b3; structure and having &#x3b3; phases distributed uniformly therein at a predetermined proportion to suppress local corrosion and induction of stress corrosion cracks.

Leadless brass alloy excellent in stress corrosion cracking resistance

Provided is a brass alloy excellent in recyclability and corrosion resistance while avoiding the addition of Bi and Si, and with which machinability is ensured and processing is facilitated with preventing inclusion of lead. The present invention includes at least 58.0 to 63.0 mass % of Cu, 1.0 to 2.0 mass % of Sn and 0.05 to 0.29 mass % of Sb and the remainder composed of Zn and unavoidable impurities. With the present invention, stress corrosion crack resistance and machinability are improved. 0.05 to 1.5 mass % of Ni is included in a copper alloy to improve stress corrosion crack resistance as a result of the interaction between Ni and Sb. Furthermore, 0.05 to 0.2 mass % of P is included to improve anti-dezincification properties.

Brass alloy and processed part and wetted part

Provided is a method for preventing the elution of Bi from copper alloy, in which the elution of Bi is prevented in leadless copper-alloy plumbing equipment and the like containing a trace of lead and a predetermined amount of Bi. The present invention relates to a method for preventing the elution of Bi from copper alloy in which at least Bi present on the surface of copper alloy containing Bi is selectively removed by preferentially dissolving Bi in a 4 to 20 mass % concentration of nitric acid while suppressing Cu dissolution. Furthermore, elution of Pb is suppressed using a 10-20 mass % concentration of nitric acid. In this case, by removing at least Bi present on the surface of copper alloy containing Bi using nitric acid and then treating the surface of the copper alloy by shot-blasting corrosive products, such as oxides, produced from the nitric acid are removed, and gloss is imparted to the surface.

Method for preventing elution of Bi from copper alloy

A copper-based alloy essentially includes 5.0 to 10.0 wt % of Zn, 2.8 to 5.0 wt % of Sn, 0.4 to 3.0 wt % of Bi, 0&#x3c;Se&#x2266;0.35 wt %, 0&#x3c;P&#x2266;0.5, one of 0&#x3c;Sb&#x2266;2.2 wt % and 0&#x3c;Ni&#x2266;4.8 wt %, and a balance of Cu and unavoidable impurities. It may essentially includes 5.0 to 10.0 wt % of Zn, 2.8 to 5.0 wt % of Sn, 0.4 to 3.0 wt % of Bi, 0&#x2266;Se&#x2266;0.35 wt %, 0&#x3c;P&#x3c;0.5 wt %, one of 0&#x3c;Sb&#x2266;2.2 wt % and 0&#x3c;Ni&#x2266;4.8 wt %, 1.20 to 4.90 Vol. % of at least one selected from the group consisting of a non-solid solution substance secured with Bi and a non-solid solution secured with Bi and Se, and a balance of Cu and unavoidable impurities.

Copper-based alloy, and cast ingot and liquid-contacting part each using the alloy

By exactly comprehending the true properties of the rare elements (such as Bi and Se) which are alternative components for Pb, the alloy is enabled to secure machinability equal to the bronze alloy (CAC406) generally used hitherto and acquire mechanical properties at least equal to the CAC406 as well in spite of a decrease in the content of the rare elements (such as Bi and Se) in the alloy. Further, it is possible to suppress the occurrence of casting defects by elucidating the unresolved influence of the decrease of the alternative components (such as Bi and Se) for Pb on the wholesomeness of a casting. Moreover, it is possible, by decreasing the rare elements, to produce a copper-based alloy containing rare elements at a low cost and to provide a cast ingot and a liquid-contacting part each using the alloy. The copper-based alloy, and the cast ingot and liquid-contacting part each using the alloy individually contain at least 2.8 to 5.0 wt % of Sn, 0.4 to 3.0 wt % of Bi and satisfying 0&#x3c;Se&#x2266;0.35 wt % to enable securing prescribed machinability and wholesomeness of a casting and exalt mechanical properties thereof.

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Yamanashi, Japan

Tomoyuki Ozasa