Table of Contents
Bronze surfacing is used for building up surfaces that have been worn down by sliding friction or other types of wear where low heat conditions prevail. This type of repair does not involve the joining of metal parts. It is merely the addition of bronze metal to a part in order that it may be restored to its original size and shape. After surfacing, the piece is machined to the desired finished dimensions. Cast iron, carbon and alloy steels, wrought iron, malleable iron, Monel, and nickel and copper-base alloys are satisfactorily built up by this process. This process is used to repair worn surfaces of rocker-arm rollers, lever bearings, gear teeth, shafts, spindle, yokes, pins, and clevises. Small bushings can be renewed by filling up the hole in the cast iron with bronze and then drilling them out to the required size.
The surface to be rebuilt must be machined to remove all scale, dirt, or other foreign matter. If possible, cast iron surfaces should be chipped to clean them. Machining will smear the surface with graphite particles present in cast iron, and make bonding difficult. If the cast iron surface must be machined, an oxidizing flame should be passed over the surface to burn off the surplus graphite and carbon before the bronze coating is applied. Hollow piston heads or castings should be vented by removing the core plugs, or by drilling a hole into the cavities. This will prevent trapped gases from being expanded by the welding heat and cracking the metal.
A neutral or slightly oxidizing flame is recommended. An excess acetylene flame will cause porosity and fuming.
A suitable brazing flux should be used to obtain good timing and adhesion of the bronze to the base metal.
The Bronze Brazing Rod bronze rod selected should fulfill the requirements for hardness and/or ductility needed for the particular application.
The bronze surfacing metal is usually applied by mechanical means. This is accomplished using two or more flames and with a straight line or an oscillating motion. A layer of bronze 1/16 to 1/4 in. (1.6 to 6.4 mm) tick is usually sufficient. It should be slowly cooled to room temperature and then machined to the desired dimensions.
References for Bronze Surfacing
Page Author: Jeff Grill