Abstract: Welding fires are one of the important causes of larger fires. This article studies the ignition mechanism and danger of non welding points during mesh structure welding operations by building an experimental platform. The experimental results show that the mesh structure welding operation can ignite a fire at non welding points, and the distance and position of the ignition points have a certain degree of uncertainty, and even multiple ignition points may occur. The ignition ability of different types of grid contact points varies. When there is a weld nugget in the middle of the contact point, the ignition ability is the strongest, and the main ignition methods are arc and splashing of molten beads resembling welding slag. The research results can provide technical basis for investigating such kinds of difficult welding fires.

Key words: welding fire, non welding operation points, welding slag, fire investigation