Experimental Investigation Of Reheat Cracking Of 2.25Cr-1Mo-0.25V Hydrogenation Reactor

With the developing trend of high parametric and large scale of equipment and to meet the requirements of new technology for cracking heavy oil or extra heavy oil, 2.25Cr-1Mo-0.25 V steel has replaced 2.25Cr-1Mo steel to be the first choice for the manufacture of hydrogenation reactor. The high-temperature strength and creep strength of 2.25Cr-1Mo-0.25 V steel have been greatly improved comparing with conventional Cr-Mo steel. Additionally, 2.25Cr-1Mo-0.25 V steel boasts the features of high-temperature temper embrittlement resistance, hydrogen embrittlement resistance and hydrogen corrosion. But in recent years, many 2.25Cr-1Mo-0.25 V hydrogenation reactors have undergo reheat cracking in fabrication and service. It has a great significance on the normal use of equipments that result in great economic losses and security risks to the related enterprises. Aiming at these problems, and with supported by “the reheat cracking research on the formation mechanism and prediction of low alloy high strength steel”, the main research works and achievements are as follows.(1) The influence of Gleeble Reheat Cracking test parameters that including the sampling location, strain rate and soaking duration has been studied by comparing test. Additionally, the mechanism for soaking duration affecting Gleeble Reheat Cracking test result was mainly analyzed by scanning electronic microscopy. Finally, the Gleeble Reheat Cracking test procedure has been perfected.(2) Aiming at the reheat cracking problem of 2.25Cr-1Mo-0.25 V hydrogenation reactors, the domestic 2.25Cr-1Mo-0.25 V steel reheat cracking sensitivity evaluation was carried out by the Gleeble Reheat Cracking test and Reheat Cracking Implant test. The result displayed that the reheat cracking susceptibility of the steel is slightly at 705℃。When the temperature is at 675℃~690℃,It is easy to occur reheat cracking,and its reheat cracking sensitive tendency is higher than conventional 2.25Cr-1Mo steel.(3) The reheat cracking of 2.25Cr-1Mo-0.25 V steel weld metal which was made by Kobelco welding material was studied by testing on thermal simulator and common high-temperature tensile testing machine. And the result displayed that its reheat cracking sensitive tendency is very low.(4) Additionally, to screen welding material from Bohler and Kobelco welding companies, the reheat cracking test was carried out to the deposited metal by using common high-temperature tensile testing machine. Both of them can meet the requirement and Kobelco welding material is a litter better about toughness.(5) Combined with the research results in this paper, the paper puts forward some suggestions to control the 2.25Cr-1Mo-0.25 V steel reheat crack in engineering application.The paper systematically carried out the work about reheat cracking for 2.25Cr-1Mo-0.25 V steel, weld metal and welding material. It can provide the basis and technical support for domestic hydrogenation reactor safety manufacture, using and follow studying.