During　the　friction　stir　welding　process,　the　motion　of　the　stirring　tool　is　divided　into　two　parts:　the　rotational　motion　and　the　lateral　feed,　both　of　which　influence　the　temperature　distribution,　material　flow,　and　slip　rate.　The　effect　of　the　rotational　motion　in　numerical　simulations　is　usually　the　focus　of　research,　but　the　changes　in　material　flow,　slip,　and　heat　generation　due　to　welding　speed　are　usually　neglected.　In　this　study,　the　numerical　model　of　stationary　shoulder　friction　stir　welding　(SSFSW)　was　developed　to　optimize　the　effect　of　welding　speed　on　heat　generation　and　material　flow　based　on　the　instantaneous　velocity　center　(IVC),　and　the　relationship　between　n/v　and　IVC　were　discussed.　The　instantaneous　velocity　center　distance　was　inversely　proportional　to　n/v,　and　its　magnitude　affected　the　difference　in　temperature　between　the　AS　and　RS.　©　2023,　The　Author(s),　under　exclusive　licence　to　Springer-Verlag　London　Ltd.,　part　of　Springer　Nature.