Dilution ratio
The ratio of the melted base material volume to the total weld metal volume. This parameter directly influences the chemical composition of the weld bead.
The melt-off rate tells you how much of the base material actually melts during welding. If you melt too much, you're dumping too much base material into the weld, which can dilute the alloying elements from the filler and make the weld brittle or porous. If you melt too little, the filler won't properly fuse with the base, giving you a cold weld without proper penetration. So you have to adjust the heat input so you cleanly fuse into the edges without the pool tipping too much. The right value depends on the material and process, but you want a uniform, controlled melt where the filler mixes well with the base.