Solutions: Cast ironSearing : Even

Solutions: Cast iron
Searing :
Even after filling there will still be graphite present in the surfaces to be joined. Graphite is a refractory material, which can inhibit “ tinning “ by playing the inner cone of an oxidising flame from the welding torch over the surfaces off the groove, most, if not all, of this graphite can be burnt away. This process, which is called “ searing” should be practiced as a matter of course before attempting to braxe weld cast iron.
Preheating
After the searing is completed, preheat the part to 300-400oC with a wide spread of heat to each side. Remember that cast iron is one of the more brittle and crack- sensitive base metals. This care should be exercised in the preheating ton ensure that it is even and uniform.
Braze welding
When braze welding cast iron the flame should be adjusted to have a slight surplus of oxygen ( oxidizing flame )
Joining is done with the filler metal unitor FC- Castiron 268S. This filler metal is extremely easy to work with, has high tensile strength and the structure and color of cast iron. Brazed connections are compact and machinable. The filler also fuses to oil impregnated cast iron.
Typical uses are brazing of cracked parts and building up worn surfaces such as gear and gear wheel teeth. The rod is flux coated and the use of additional flux is not necessary.
Heat the starting point to a dark red heat. Touch the rod to the surface and melt off a little of the flux coating. Then melt off drop from the rod into the groove and spread it out by continually moving the torch, which should be held flat at an angle of about 15-30 o to the workpiece, and approximately 1 cm above the groove. When the filler has flowed freely into the seam, melt off a new drop and repeat the procedure.
Do not stir the weld pool with the rod. The base material shall not melt.
When the brazing work is completed, the part should be allowed to cool slowly in kieselgur or dry sand. Surplus flux must be removed by hot water and brushing.
Alternatively, where a hardwearing surface is required, the Joining can be done wih the filler rod Unitor FC- Wearbro 262, applying the same technique as described for FC- Castiron 268S.
Unitor FC- wearbro 262 has a low bonding temperature. However, the strength and machinability is lower than for FC- Castiron 268S.
Technical details on the rods are found in the section “ consumables “