Temporary bolts are often inserted in a few holes as. an alinement aid and 



to help draw the structural steel members together. Steel rivets are 



o 



usually driven hot by heating to 582 Celsius (1 8QQ Fahrenheit). During 



driving a second head is formed and the rivet shank may be expanded to fill 



the hole. As the rivet cools, it shrinks and squeezes the connected pieces 



together. The magnitude of this clamping force depends on the driving and 



finishing temperature of the riveting operation, the overall grip length, 



and the driving pressure. Because these are variables that are difficult to 



control, no credit may be claimed for clamping force in design calculations. 



Riveting is used to advantage in joining aluminum structural alloys that 

 have been heat treated for greater strength. The high heat encountered in 

 welding reduces the strength of heat-treated aluminum. Less skill is re- 

 quired for riveting than for welding. The specification covering wire and 

 rod to he used in aluminum rivet manufacture is ASTM Standard B316-75, 

 Aluminum-alloy Rivet and Cold-Heating Wire and Rods. Of the listed alloys, 

 alloys 1100, 3003, 5005, 5052, 5056, and 6061 are most suitable for joining 

 aluminum alloys in coated structures. The 6061 alloy is the only alloy that 

 can be heat treated to obtain higher strength levels. 



Bolts are made from bar stock. High strength steel bolts are made by 

 open-hearth, basic oxygen, or electric furnace process. They are fine- 

 grained and must meet ASTM Standard A588-75. The atmospheric corrosion 

 resistance of this steel is approximately two times that of carbon structural 

 steel with copper. High strength bolts are made using various types of 

 quenching and tempering processes and are used in structural connections 

 where high stress and corrosion resistance are required. 



Bolts are used to advantage in structural installation where welding is 

 not practical and where working connections are necessary such as tongue and 

 groove pile connections, bulkhead wales, and tiebacks. It is common practice 

 to oversize bolt requirements in marine exposures as an allowance for exces- 

 sive metal loss from corrosion. 



b. Welding . Welding processes most likely to be used during coastal 

 structure construction include gas welding, arc welding, and thermite welding. 

 Other processes, such as resistance welding, friction welding, and induction 

 welding, are used during fabrication of mechanical and electrical equipment. 

 Each welding process has areas of application where its use is the most 

 economical for the desired level of quality. 



Gas welding is classified by the gases used; i.e., air-acetylene, oxy- 

 acetylene, oxy-stabilized methylacetylene-propadine, and oxy-hydrogen. The 

 oxyacetylene flame has the highest temperature, about 3 371 v Celsius (6 100 

 Fahrenheit), that can be obtained with commercially available gases. Because 

 the temperature produced by the oxyacetylene flame is far above the melting 

 point of most metals, rapid localized melting necessary for welding is 

 produced. 



Oxyacetylene is suitable for welding carbon and alloy steel, cast iron, 

 copper, nickel, aluminum and zinc alloys. Lower melting temperature alloys, 

 such as aluminum, magnesium, zinc, lead and some precious metals, can be gas 

 welded using hydrogen, methane, or propane fuel gases. Gas welding is not 



214 



