Method of laser butt welding

A method of forming a laser butt weld comprising the steps of providing two members to be butt welded, positioning respective longitudinally extending edges of said members to be butt welded in abutting contact with the two members being canted slightly with respect to one another so that the butt joint formed by said abutting edges is open toward a first side of said members in a direction transverse to the direction in which said edges longitudinally extend and with said abutting edges of said butt joint contacting one another toward a second side of said members opposite said first side, directing at least one high energy density laser beam at said butt joint while moving at least one of said laser beam and said members relative to the other in a direction along said butt joint for progressively butt welding said members, said laser beam being directed at said joint from said first side of said members in a direction transverse to the direction in which said edges longitudinally extend so that at least a portion of said laser beam extends into the open side of said butt joint and penetrates completely through said butt joint to form a keyhole therethrough with molten material of said members surrounding said keyhole, and urging said two members in the direction of said butt joint during said welding so that the molten edges of said members are mashed together immediately behind the keyhole as said keyhole and laser beam are moved relative to said members in a direction along said butt joint.