Could someone tell me the thermal conductivity of A 106 B, A 106 C and A 285 C. And also the sourse. Are these metal acording to US standards? ANSI? Tnx.

The materials are essentially low carbon steels and have the same coefficient of thermal conductivity. 30 Btu/hr. ft. Deg F at 70F (121 Watts/m Deg C) is a reasonable figure. My reference is the TEMA (Tubular Exchanger Manufacturers Association) Code, Table D-12. There are other references which will give similar data.

The materials you mentioned are per ASTM standards.