Friction welding is one of solid state welding method, friction welding uses the heat from friction between two materials to join them. The purpose of this research is to analyze the effect of friction time to microstructure, hardness vickers and tensile strength of the material.. This research use sylindrical stainless steel 304 and low carbon steel St 42 with 20mm big diameter and 14mm small diameter . This research uses variation of friction time (3,6,9,12 second) as its parameter. Machine’s rotational speed for this friction welding is 1000 rpm, friction pressure is 30 MPa and upset pressure 60 MPa. the test that used ini this research is microstructure, hardness vickers and tensile strength. This research found a hypothesis that the longer friction welding duration, the denser of microstructure grain threfore the hardness vickers is higher, in additionthe longer friction welding duration, the lower the tensile strength. The highest hardness vickers with hardness value 302.8 VHN found on a joint with friction time 12 second. The lowest hardness vickers with hardness value 167 VHN found on a joint with friction time 3 second. The highest tensile strength with tensile strength value 556.235 MPa found on a joint with friction time 3 second. The lowest tensile strength with tensile strength value 289.392 MPa found on a joint with friction time 9 second.