The tube of ethylene cracking furnace, specification: φ70×7mm, material: HP45Nb, the lower end of the tube cracked after 6 years of service.

The hysteresis nondestructive evaluation technology was used to measure and evaluate the furnace tube, and the Hc of the new tube was 0.1A /cm. Hc=1.5 A/cm in the part with carburizing damage but not cracked; The cracking caused by severe carburizing damage was Hc=2.9 A/cm.

          The Hysteresis nondestructive evaluation technology, no need to cut pipe, no need to polish the workpiece surface, can be directly measured and evaluated on the spot, data collection only 3 seconds, is the only feasible new technology for nondestructive evaluation of furnace tube carburizing damage.