Older International truck specification as an example of what the manufacturer service manual will say :
TRUCK SERVICE MANUALTM 5-4210-230-14&P-1FRAMESb.Preheat the frame rail along the crack area to500-600 degrees to burn off excess oil or paintthen permit heated area to cool to 200degrees or below before welding is started.Under no circumstances should the rail beheated to a temperature exceeding 900-950degrees F. since this is the temperingtemperature of the rail.c.Either alternating current or direct currentreversed polarity, combined with a short arcand a beading or narrow weave techniquemay be used. Direct current reversed polarityis recommended or preferred.d.Slag should be removed after each pass andan interpass or constant temperature of 200degrees should be maintained.e.When sufficient metal has been deposited, theweld bead should be ground flush, Fig. 7, withthe surface being repaired.Fig. 7.f.Where both sides of the frame rail areaccessible, a V-groove is ground from the sideopposite the repair and the procedure outlinedabove repeated. Dependent uponaccessibility, "chill" strips should be usedwherever possible. The V-groove ground onthe opposite sideof the repair should be deep enough to enter the sound metalof the first weld repair "C" of Fig. 7.FrameWelds on heat treated material tend to reduce physicalproperties in the weld heat-affected zone. Because of this, itis recommended that all reinforcements be designed so thatall welds are parallel, rather than perpendicular to the frame rail edges. Welds perpendicular to the flange edges will reduce the carrying capacity of the rail, Fig. 8 and 9. Fig. 8 The edge of the reinforcement flange to the edge of side rail flange dimension should be held to a minimum of three quarters of an inch to keep the heat-affected zone from extending to the sidemember flange edge. Wherever possible, it is recommended that plug welds of the type shown in Fig. 9, be substituted for edge welds when assembling the reinforcement to the side rail. Plug welds offer the advantages of a reduced heat-affected zone plus increased flexibility and reduced stress concentrations. When using this method, one half inch (minimum) diameter holes should be drilled and chamfered in the reinforcement on 2" center to center distances. At no time should these holes be drilled in the frame rail being repaired. The reinforcement should then be installed in its proper position on the sidemember and the holes filled with weld material. Again a minimum dimension of 3/4" should be maintained between the weld and the edge of the sidemember flange. The voltage, amperage and pre-heat specifications listed below should be followed. CTS-2037-A Page 6