When do I use Tech-Rod® 99, Tech-Rod® 55 and Ferroweld® electrodes?
Choosing electrodes for welding cast iron typically comes down to three things: cost, machine-ability, and whether the weld is single or multiple pass.
Tech-Rod 99 (AWS class ENi-CI) is a nominally 99% Nickel electrode. Nickel is expensive, and so, therefore, is this premium electrode. The electrode will deposit welds that are machine-able, an important consideration when the casting is to be machined after welding. Repairs made with Tech-Rod 99 are often single pass welds with high admixture. Even with high admixture, the weld deposit will remain machine-able. It works best on castings with low or medium phosphorous contents.
Tech-Rod 55 (AWS class ENiFe-CI) is a nominally 55% Nickel electrode. The lower Nickel content makes this electrode more economical than Tech-Rod 99. Weld deposits are usually machine-able, but under conditions of high admixture, the welds can become hard and difficult to machine. It is often used for repairing castings with heavy or thick sections. As compared to Tech-Rod 99, welds made with 55 Ni are stronger and more ductile, and more tolerant of phosphorous in the casting. It also has a lower coefficient of expansion than 99Ni, resulting in fewer fusion line cracks.
Ferroweld (AWS class ESt) is a lower cost, steel electrode. The weld deposits are hard, and are not machine-able, but can be finished by grinding. This is the lowest cost electrode for welding cast iron, and the electrode has a very user-friendly arc. It can tolerate welding on castings that cannot be completely cleaned before welding. Ferroweld deposits will rust, just like cast iron. This may be important when repairing cast iron parts such as exhaust manifolds on antique cars.