Post fire tensile properties of S355 J2 structural steel welded connections for construction industrial applications

Constructional steel structure stability during its service and post fire effect on steel after major fire exposure is very detrimental and critical on the parent metal (PM) un-welded region and welded connections. Existing literatures on residual material properties of various constructional steels have exhaustive focused only on the mechanical properties of PM. This paper presents the comparative results of S355 J2 structural steel joints made by GMAW and FCAW after fire exposure up to 900 degrees C. The residual properties were evaluated after elevated temperature fire exposures to 300 degrees C, 600 degrees C and 900 degrees C, respectively. Experimental results shows at 300 degrees C, the residual mechanical properties such as yield strength (YS), ultimate tensile strength (UTS) and hardness revealed small increment, while after 300 degrees C trend follows a detrimental pattern in YS, UTS and hardness irrespective of process used. The increment in strength and hardness properties at 300 degrees C could attribute to the strain hardening and blue brittleness effect on PM and welded connections. Moreover, experimental results confirmed that welded connections obtained from high strength steel grade S355-J2 begin to deteriorate strength at temperatures above 300 degrees C. The reduction in tensile and hardness of post fire condition is analyzed with respect to post fire microstructural changes. The results observed in this study may be useful for constructional steel industries.

Automated summary

This paper presents comparative results of residual properties of S355 J2 structural steel joints made by GMAW and FCAW after fire exposure. The results show that at temperatures below 300 degrees C, the mechanical properties of the steel increase, but at temperatures above 300 degrees C, regardless of the welding process used, the properties show a detrimental trend. The increase in strength and hardness at temperatures below 300 degrees C may be attributed to strain hardening and brittleness effects. Moreover, welded connections obtained from high strength steel grade S355-J2 begin to deteriorate strength at temperatures above 300 degrees C.