CLASSIFICATION

írod-CI is an oxy-fuel (oxyacetylene) gas welding rod which is used for welding ordinary machinable gray iron casting may vary from 140 to 280 MPa tensile strength, and 150 to 250 Brinell hardness. The use of a gray iron welding rod for oxyfuel gas welding can produce a machinable weld metal of the same color, composition, and structure as the base metal. The weld, if properly made, may be as strong as the original casting.

írod-CI welding rods are used for filling in or building up new or worn castings, and for general fabrication, salvage, and repair.

Post weld Heat Treatment: PWHT may also be used to improve the machineability of the heat-affected zone adjacent to the weld metal. Tempering beads sometimes are employed to achieve the desired improvement. These beads, consisting entirely of filler metal and a previous bead, are made in such a manner that the heat input tempers any martensite present from a previous bead.

Recommendations

• • Pre-heat of 595-650°C generally required.
  • Post-heating varies with the size of the casting: slow cooling, complete stress relief 620°C or full annealing 900°C.
  • Gas welding produces less hardening in the HAZ than does arc welding.
  • Readily machinable.
  • Porosity can be minimized by using a slightly reducing flame.
  • The RCI rod contains enough Si and C to replace those elements lost through welding process.
  • Use METAFIL Cast Iron Flux.

CHEMICAL COMPOSITION OF UNDILUTED WELD METAL

Single values shown are maximum, unless otherwise noted. *Nickel plus incidental cobalt. #Copper plus incidental silver.

ALL-WELD-METAL MECHANICAL PROPERTIES

Welding Considerations

The casting skin should be removed from the weld area by machining, grinding, chipping or other suitable means. When repairing casting defects, care should be exercised to ensure removal of any defective metal to sound base metal before welding. Also, all oil grease, dirt, or other foreign material should be eliminated using suitable solvents. If oil, grease, or solvents have impregnated the casting, heat should be applied to the area to be welded until volatilization is no longer observed. A temperature of 400°C generally is sufficient for this operation. If the casting is too greasy, flash heating the welding surfaces to about 540°C should drive off the grease in a gaseous state.

Castings to be welded with a V-groove should have the edges beveled to form a 60 to 90 degree include angle. The groove should have a root face greater than zero, so that there is less difficulty in aligning the joint members and there is no melting through of the entire thickness.

Next, the casting should be preheated as a whole, or locally in critical sections, if a closed or rigid construction is involved. Ideally this involves preheating the entire casting to 430 to 566°C, or in the case of alloy castings, as high as 677°C. Preheating not only tends to equalize expansion and contraction stresses and ensure the machinability of the final weld, but also enables the weld to be made more rapidly. Such preheating preferably should be done in a charcoal fire or a furnace. In the case of small castings, however, preheating with a welding torch may be employed.

A neutral oxyfuel gas flame is preferred for welding cast iron. Some authorities, however, recommended the occasional use of a reducing flame where decarburization is to be avoided. A flux is required. The purpose of the flux is to increase the fluidity of the iron silicate slag that forms on the weld pool.

After the groove has been beveled and cleaned, and the casting preheated, the welding torch is directed over an area extending 25 mm around the weld until the entire area is a dull red. Then the flame is directed at the bottom of the groove, keeping the tip of the cone 3.2 to 6.4 mm from the metal, until a weld pool approximately 25 mm long has been formed.

The flame is then gradually moved from side to side until the groove faces begin to melt into the weld pool. The flame is directed on the rod, and filler metal is added to the weld pool. The groove faces are melted ahead of the advancing pool. The thickness of each layer of weld metal should not exceed 9.5 mm.

In the case of rigid structures requiring extensive machining, it is advisable to stress relieve at the preheat temperature after welding. In any case, the casting should be allowed to cool slowly by furnace cooling, or by covering it with, or immersion in, an insulating material such as dry sand.

Preheating is especially helpful in overcoming the differential mass effect encountered when welding a thick to a thin base metal. The use of preheat in conjunction with welding for pressure tightness also increases the resistance to cracking at the weld interface. Judicious use of preheating when welding cast iron will permit the weld and surrounding area to cool at a more uniform rate.

ELECTRODE SIZE & WELDING CURRENT (OFW)

WARNING: Safety and health information is available from many sources, including, but not limited to Safety and Health Fact Sheets listed in A11.3, ANSI Z49.1 Safety in Welding, Cutting, and Allied Processes published by the American Welding Society, 8669 Doral Blvd., Suite 130, Doral, FL 33166., and applicable federal and state regulations. The Safety and Health Fact Sheets are revised, and additional sheets added periodically.