Severe　spattering　is　one　of　the　common　problems　during　fiber　laser　keyhole　welding.　In　this　study,　the　correlation　between　the　spatter　formation　and　laser-induced　evaporation　vapor　on　the　front　keyhole　wall　(FKW)　was　studied　by　changing　the　welding　speed　during　fiber　laser　keyhole　welding.　The　spatters　were　mainly　generated　in　front　of　and　behind　the　keyhole　mouth,　and　the　diameters　of　spatters　were　mainly　between　50-100　mu　m　at　low　welding　speed,　while　the　diameters　of　spatter　particles　were　mainly　between　100-150　mu　m　at　high　welding　speed.　As　the　welding　speed　was　increased,　the　tilt　angle　of　the　FKW　decreased　gradually,　and　the　main　spatter　generation　position　shifted　from　in　front　of　the　keyhole　mouth　to　behind　the　keyhole　mouth.　In　low　welding　speed,　the　spatter　velocity　was　higher　than　that　in　high　welding　speed.　Further　analysis　shows　that,　the　recoil　pressure　of　laser-induced　evaporation　squeezed　the　molten　metal　layer　in　the　FKW　to　generate　spatters　in　front　of　the　keyhole　mouth　in　low　welding　speed.　In　high　welding　speed,　the　decrease　of　the　molten　metal　layer　in　the　FKW　led　to　the　decrease　of　spatters　in　front　of　the　keyhole　mouth;　however,　the　laser-induced　evaporation　vapor　from　the　FKW　was　more　liable　to　impact　the　rear　keyhole　wall　to　generate　spatters　behind　the　keyhole　mouth.　(C)　2020　The　Authors.　Published　by　Elsevier　B.V.