The Study Of Cold Cracking Susceptibility Of 11MnNiCrMoV Steel Plates

Although a lot of researches on the hydrogen-induced cracks (HIC) of high strength low alloy steels (HSLA steels) have been being done over all worlds for many years, how to avoid the occur of HIC for engineering structure still is the most noticeable problem. Cracks would not occur in the weldments only using the rigorous welding processes for welding of high strength steels of large-scaled complicated structures like ship structures. The rigorous welding processes lead to increase of welding cost and worsening of work conditions of welders. Therefore improvement of weldability of the HSLA steels and reduction of the requirements of welding processes by taking the various ways are the pursued aim in the welding research of large-scaled complicated structures.11MnNiCrMoV steel is a high strength ship structural steel which its yield strength is not less than 440MPa. The steel plates possess the good properties of lower temperature toughness and anti-corrosiveness of sea-water. The weldability of the steel had been improved after its chemical composition was modulated, but its requirements of welding processes is the same as the initial requirements of the 11MnNiCrMoV steel in the first stage. The rigorous welding processes produced some difficulties in the ship-building.Diffusible hydrogen of the weldments is one of the three-affecting-factors on formation of HIC. Among the shielding metal arc welding (SMA), submerged arc welding (SAW) and gas shielding welding, SMA possesses more content of diffusible hydrogen and is prone to produce HIC than others. The proneness of HIC would be reduced while the contents of diffusible hydrogen in the SMA electrodes were reduced using the effective ways. E5515-G electrodes are used specially for welding 11MnNiCrMoV steel. Under the weldability of 11MnNiCrMoV steel had been improved, the paper puts forward the conclusion that proper boost of the barking temperature of E5515-G electrodes will be in favor of reduction the contents of diffusible hydrogen of the electrodes and not affect the its properties according to the study of affecting-factors on the diffusible hydrogen of E5515-G electrodes. Environ-ment temperature and relative humidity all affect the contents of diffusible hydrogen of the electrodes. The absolute humidity (water content in the air) in the air is the sole Environmental factor affecting contents of diffusible hydrogen. When the absolute humidity is large, the air intruding the arc becomes the main source of diffusible...