[Soldering of a low gold content alloy (46%)]. / Esutdo da soldagem de uma liga com baixo conteúdo de ouro (46%).

This is the third part of a research about a low gold content alloy (Au 46%, Pd 4%, Ag 40%, Cu and Zn), involving the study of soldered joints. Transverse test was used to evaluate mechanical resistance of bars joined by soldering. Comparativily were considered the following "soldering" condution: entire bars without investing and without soldering; entire bars with investing and without soldering but simulating thermal cycle and quenched in water after one and five minutes; with investing, soldering and quenched in water after one and five minutes. Of the "soldered" alloy were obtained also Brinell and Vickers hardness numbers. Corrosion resistance test was performed for six month at vapors of acetic acid solution, saturated with hydrogen sulfide. From the results it was possible to conclude: the soldered joints of the alloy reach good corrosion resistance; the soldered joints do not become brittle; thermal cycling as elapsed from soldering procedure and water quenched after five minutes increases the strength of the alloy and the soldered joints.

[Mechanical, physical and corrosive properties, and relative cost of a low gold content alloy (46%)]. / Propriedades mecânicas, físicas e de corrosão, e custo relativo de uma liga com baixo conteúdo de ouro (46%).

The research presents some properties of a low gold content (46%) alloy. Mechanical properties were performed with specimens submitted to several treatment; as cast; hardened at 400 degrees C/15 min; softened at 700 degrees C/10 min; and hardened after softening. Melting temperature was considered when the alloy become a liquid sphere. Casting shrinkage determination was based on the method presented by EARNSHAW. Density was obtained by the weight of polished specimens in and out of water. Corrosion was tested at vapors of acetic acid solution, saturated with hydrogen sulfide, for a period of six months. Cost was computed on base of materials cost and density of alloy. The results showed: tensile strength and proportional limit are very high, specially when hardened and the alloy may be used for large bridges; elongation is low when alloy was heat hardened, but is good when in the as cast condition; the alloy may be handled with conventional materials and equipment; corrosion resistance is excellent; final cost is a little higher than half that of conventional gold alloy.