Weld metal based on Monel alloy 400 with raised levels of Mn and Ti to suppress hot cracking and porosity. For welding alloy 400 and similar parent material to itself and to others in the Ni-Cu alloy system, such as pure nickel and cupronickel. Welds in alloy K500 are satisfactory but cannot match the strength of this precipitation-hardened alloy. Castings of alloy 400 with 1.5 %Si or higher are subjected to HAZ cracking. For dissimilar joints between alloy 400 and other alloys or steels, sensitivity to dilution by Fe (20-30%) or Cr (3- 6%) can lead to low ductility in weld metal close to the fusion boundary. Direct welds to mild or low alloy steels are satisfactory with dilution control, although ERNiCr-3 wire is preferable and necessary for stainless and higher chromium alloys. Alloy 400 has a useful combination of strength, thermal conductivity and resistance to corrosion by seawater, inorganic salts, sulphuric and hydrofluoric acids, hydrogen fluoride and alkalis. Applications include **heat exchangers, piping, vessels and evaporators in the offshore, marine, chemical, petrochemical and power engineering industries**. No preheat required, maximum interpass.