Silicon Bronzes

Containing up to 3% silicon, silicon bronzes are characterized by high mechanical and antifriction properties. They are made in all wrought forms. 

These alloys have corrosion resistance similar to that of copper, with mechanical properties equivalent to mild steel. Because silicon bronzes do not generate sparks under shocks, they can be used in the fabrication of explosion-proof equipment. Compared to tin bronzes, the tinless bronzes have a higher shrinkage (1.7-2.5% against 1.3-1.5% of tin bronzes) and less fluid-flow, which is an important consideration in designing. 

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Table 19. Conductivity and H04 (Hard) Temper Tensile Properties of Silicon Bronze Alloys...

Table 13. Properties of Silicon Bronze and Silicon Brass Alloys...

Clad tube eets in service with carbon steel backer material include stainless-steel types 304, 304L, 316, 316L, and 317, Monel, Inconel, nickel, naval rolled brass, copper, admiralty, silicon bronze, and titanium. Naval rolled brass and Monel clad on stainless steel are also in service. 

Yellow brass Admiralty brass Aluminum bronze Red brass Copper Silicon bronze 70-30 cupronickel Nickel (passive)... 

Copper and silicon bronze 0 5 2 3 < 400 2 < 750 Wronglit, cast, clad ... 

Bronzes are somewhat similar to brasses in mechanical properties and to high-zinc brasses in corrosion resistance (except that bronzes are not affected by stress cracking). Aluminum and silicon bronzes are very popiilar in the process industries because they combine good strength with corrosion resistance. 

Copper-alloy corrosion behavior depends on the alloying elements added. Alloying copper with zinc increases corrosion rates in caustic solutions whereas nickel additions decrease corrosion rates. Silicon bronzes containing between 95% and 98% copper have corrosion rates as low as 2 mil/y (0.051 mm/y) at 140°F (60°C) in 30% caustic solutions. Figure 8.2 shows the corrosion rate in a 50% caustic soda evaporator as a function of nickel content. As is obvious, the corrosion rate falls to even lower values as nickel concentration increases. Caustic solutions attack zinc brasses at rates of 2 to 20 mil/y (0.051 to 0.51 mm/y). 

Figure 6.16. Stress-strain of shock-loaded silicon bronze contrasted to the annealed alloy showing evidence of a Bauschinger effect.

Figure 6.17. VISAR wave profiles of copper and silicon bronze at 10 GPa exhibiting differing unloading wave shapes supporting a Bauschinger effect contribution to unloading.

For a given amplitude of the quasi-elastic release wave, the more the release wave approaches the ideal elastic-plastic response the greater the strength at pressure of the material. The lack of an ideally elastic-plastic release wave in copper appears to suggest a limited reversal component, however, this is much less than in the silicon bronze. Collectively, the differences in wave profiles between these two materials are consistent with a micro-structurally controlled Bauschinger component as supported by the shock-recovery results. Further study is required to quantify these findings and... 

Chlorides—Maximum 750 ppm (as KaCl) for galvanized steel maximum 1,500 ppm for Type 300 stainless steel maximum 4,000 ppm for Type 316 stainless steel silicon bronze is the preferred material if chlorides exceed 4,000 ppm. 

Silicon-bronzes Silicon-bronzes usually contain 1-5-3% Si and 0-5-1% Mn. They are used in wrought or cast form, though the cast alloys may also contain some Zn and Fe. 

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