Welding, Brazing, or Soldering

Porous P/M products can be sinter bonded to soHd metals. They can also be welded, brazed, or soldered. Filling the voids with flux or molten metal has to be avoided. P/M porous products can be machined, but blocking of the porous passages has to be avoided. Press fitting and epoxy bonding are commonly used. 

Branch Welds These welds eliminate the purchase of tees and require no more weld metal than tees (Fig. 10-127). If the branch approaches the size of the run, careful end preparation of the branch pipe is required and the run pipe is weakened by the branch weld. See subsection Pressure Design of Metallic Components Wall Thickness for rules for reinforcement. Reinforcing pads and fittings are commercially available. Use of the fittings facilitates visual inspection of the branch weld. See subsection Welding, Brazing, or Soldering for rules for welded joints. 

If material is welded, brazed, or soldered, the allowable stress values for the annealed condition shall be used. 

Stainless steels are iron-based alloys which contain more than 12% chromium. A common composition contains 18% Cr and 8% Ni, and is designated as either 18 8 or type-304 stainless steel. Unlike ordinary carbon steel, the stainless steels in the 300 series do not become brittle at low temperatures. Stainless steel has a rather low thermal conductivity. It may be welded, brazed, or soldered and is machinable with some difficulty. Type 303 is the easiest to machine. 

Chlorine, sulfur and zinc are potentially harmful chemical elements. Paints and crayons used to mark susceptible alloys must contain low quantities (measured in parts per million, or ppm) of the harmful chemical elements. Less than 100 ppm is allowable. Even if approved marking materials are used, they should be removed from areas that are to be welded, brazed or soldered. An approved solvent such as a non-chlorinat-ed type should be used to remove marking materials. The same principles apply when adhesive-backed tapes are used to fix items to stainless and nickel alloy products (e.g., for radiography). All traces of adhesive must be removed from the surface with an approved solvent. There are no restrictions on using fiber tip markers because they do not leave solid residue. Solvent removal is not required with fiber tip markers. 

Plastic can be joined with an appropriate solvent. Metal may be welded, brazed or soldered, but the most popular method of on-site joining of metal on electrical installations is by nuts and bolts or rivets. 

Almost any method of joining is plicable to aluminum riveting, welding, brazing, or soldering. A wide variety of mechanical aluminum fasteners simplifies the assembly of many products. Adhesive bonr of aluminum parts is widely employed, particularly in joining aircraft components. 

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