Seat frame of a motor vehicle seat with two side parts and a transverse tube

The seat frame has a left and a right link (20, 22), a left and a right side part (30, 32) and a transverse tube (24) which connects the two side parts (30, 32). The links (20, 22) are connected to the transverse tube (24) for conjoint rotation. The transverse tube (24) has a main tube (42) located between the side parts (30, 32), a left end piece (44) assigned to the left side part (30) and a right end piece (46) assigned to the right side part (32). The main tube (42) is connected to the two end pieces (44, 46) in respective overlapping regions (50, 52). The main tube (42) is manufactured from a material, preferably from steel, which has an at least 20% higher tensile strength than the material of the end pieces (44, 46).