Experimental Study on the Welding Mechanical Properties of Steel Truss Structure of Coal Conveying Trestle in Coal Preparation Plant

In response to the welding mechanical performance issues of the steel truss structure of the coal transportation wharf in the coal preparation plant, this study conducted proportional welding tests on the Q345 steel truss using carbon dioxide gas shielded welding technology to systematically investigate the influence of welding process parameters on the structural bearing performance. Firstly, the bearing capacity of the welded joints was tested through axial compression and axial tension tests. The results showed that the average compressive and tensile bearing capacities of the test samples were 5278.65 kN and 5071.68 kN, respectively, which were significantly higher than the JG/T11-2009 standard values. However, local measuring points experienced mechanical performance fluctuations due to softening of the welding heat affected zone or weld defects. Secondly, the influence of welding groove angle on the stress distribution and deformation of the structure was studied. It was found that the stress concentration effect was minimal at a groove angle of 70 °, with a transverse shrinkage of only 1.2 mm. The longitudinal bending deformation was optimized to 1.2 mm, resulting in the best comprehensive mechanical performance. Finally, the relationship between welding heat input and strength was analyzed, and it was shown that the compressive strength and tensile strength reached their peak values when subjected to a heat input of 41 kJ/cm. Low heat input can easily lead to incomplete fusion defects, while high heat input can cause grain coarsening and softening effects. The research results provide key parameter basis for optimizing the welding process of steel truss for coal transportation wharf, which can significantly improve the service safety and durability of the structure.