Welding Carbon Steel Requirements. The carbon content is most important. When matching strength is not a requirement standard electrodes such as E7018 and ER70S-6.
PWHT of carbon steels greater than 34 thick is not always a requirement. Based on yield strength for carbon steel in groups 1 2 and 3. Up to about 025 C no special problems in Welding-steel should be found.
When welding of Medium carbon steel with Oxyacetylene welding An excess of acetylene is used in the gas flame to obtain sufficient heat No flux is needed when employing oxy-acetylene welding.
Class 2 Welding of Carbon Steel Pipework BS 2971 1991 Austenitic Stainless Steel Pipework BS 4677 1984 Approval of testing of welders for fusion welding of all comply with BS EN 287. If you really would like to weld plain carbon steel to low alloy steel the PWHT should be carried out. I recommended 710-740 Degree C. The best practice would call for welding in the annealed condition and then to provide for heat treatment if required and possible.