This paper presents thermomechanical fatigue tests of 16Mo5.3b steel test specimens, in temperature range 60oC÷540oC, with total strain control in wich cycle of temperature variation, on ring surface test specimens. Thermal condition of test is without soaking period at maximum temperature 540oC. Using a modern process of experimental datas statistical analysis is tracing the material thermomechanical fatigue curve, and base on this is established the shell type structures durability, like coking chambers.