250 



Copper and Copper-base Alloys 



70 75 80 85 90 95 100 105 110 115 

 Rockwell F Hardness !/i6"Bcill eOKg.Loord 



Chart 33. — This chart can be employed to determine the approxi- 

 mate tensile strength and percentage elongation of Type B sUicon- 

 bronze strip (2.10% silicon, 0.24% tin, balance copper) when only 

 Rockwell hardness is known. It is accurate for all thicknesses between 

 0.020 and 0.080 in. 



■R120 



:ioo 



= 80 



^ 70 



60 



50 



40 



50 



o 20 



CD 550 600 700 800 900 1000 1100 1200 1300 1400 

 Annealing Temp. in Deg.Ff 1 Hr.a+ Tenip.) 



Chart 35. — The effect of annealing on the Rockwell hardness, 

 percentage elongation in 2 in., and grain size of Type B silicon-bronze 

 tubing (0.25% tin, 1.91% silicon, balance copper), previously cold- 

 drawn 70 per cent (reduction of area). 



CD 550 600 700 800 900 1000 1100 1200 1300 1400 

 Annealing Temp, in Deg.F. (IHr a+ Temp.) 

 Chart 34. — The effect of annealing on the tensile strength and 

 apparent elastic limit of Type B silicon-bronze tubing (0.25 % tin, 

 1.91% silicon, balance copper), previously cold-drawn 70 per cent 

 (reduction of area). 



JOINING THE TYPE A SILICON BRONZES* 



As has been mentioned, the sUicon bronzes owe much 

 of the popularity they enjoy to the fact that they are 

 weldable by all the common methods. Welded applica- 

 tions of the silicon bronzes include range boilers or hot- 

 water storage tanks, paper-mill pulp lines, unfired 

 pressure vessels to meet ASME Specifications (Par. U69 

 and U70, Case 864) and linings for steel vessels. 



The silicon bronzes are, to sum up briefly their metal- 

 lurgical characteristics as they affect weldabUity, high- 

 shrinkage aUoys of medium thermal and electrical 

 conductivity with a hot-short range just below their 

 melting points. Indicative of their low strength when 

 hot is the fact that hot working is not recommended at 

 temperatures above 1475°F. In the liquid state they 

 are comparatively free flowing but are usually covered 

 with a thin film of silicon oxide, which materiallj^ 

 increases their surface tension. Such reducing flame 

 gases as carbon monoxide and hydrogen are quite 

 soluble in molten silicon bronzes. 



Rapid freezing of the weld metal is recommended to 

 promote a fine grain structure, to prevent overstressing 

 of the weld metal while it is in a weak temperature range, 

 and generally to cut down the exposure time to con- 

 taminating flame and ambient air gases. 



Although all the common methods of fusion welding — ■ 

 carbon arc, metal arc, and oxyacetylene — ^have been 

 employed, the carbon arc and oxyacetylene methods find 



*By J. R. Hunter, Research Department, Revere Copper & 

 Brass, Inc. 



