A method of manufacturing a welded steel part, comprising the steps of: i) supplying a first and a second steel sheets, at least one of the first and second steel sheets being made of a steel substrate and comprising a coating of aluminum alloy, being characterised in that at least one of the first and second steel sheets is hot-press formed, and by the following: ii) deforming the peripheral edge of the second steel sheet to create an end portion (3a1) which is extended by an inclined junction portion (3a2) to a welding portion (3a3), iii) positioning a peripheral edge of the first sheet above, and on or near an upper face (3a11) of the end portion (3a1) of the peripheral edge of the second sheet so as to create a groove laterally delimited by at least one part of an upper surface (3a21) of the inclined junction portion (3a2) of the peripheral edge of the second sheet and an edge (2a3) of the peripheral edge of the first sheet, the inclined joining portion (3a2) extending by a welding portion (3a3) in longitudinal continuity with the peripheral edge of the first sheet, • wherein the longitudinal continuity is defined by a longitudinal alignment of at least part of a mid-thickness zone of the welding portion (3a3) with at least part of a mid-thickness zone of the peripheral edge of the first sheet, and • wherein the longitudinal alignment of the mid-thickness zones (6,7) is defined by the position on the edge (2a3) of the peripheral edge of the first sheet of a projection point of at least one straight line which is parallel to the mid-thickness surface zone of the second sheet and which is located in the corresponding mid-thickness zone, said position being located within the mid-thickness zone of the first sheet, • wherein each said mid-thickness zone (6,7) is defined in cross section by a zone (H 21,H 31) centred on the mid-thickness (6a,7a) of the corresponding sheet (2,3), having a thickness equal to 40% of the thickness of the respective sheets or. iv) welding the first and second steel sheets thus positioned by using a filler wire which is deposited in the groove previously made, wherein said welding wire, after melting and cooling, constitutes a weld bead connecting the first sheet to the second sheet and being part of said welded steel part, the end portion (3a1) of the peripheral edge of the second sheet being a welding support sheet, i) supplying a first and a second steel sheets, at least one of the first and second steel sheets being made of a steel substrate and comprising a coating of aluminum alloy, being characterised in that at least one of the first and second steel sheets is hot-press formed, and by the following: ii) deforming the peripheral edge of the second steel sheet to create an end portion (3a1) which is extended by an inclined junction portion (3a2) to a welding portion (3a3), iii) positioning a peripheral edge of the first sheet above, and on or near an upper face (3a11) of the end portion (3a1) of the peripheral edge of the second sheet so as to create a groove laterally delimited by at least one part of an upper surface (3a21) of the inclined junction portion (3a2) of the peripheral edge of the second sheet and an edge (2a3) of the peripheral edge of the first sheet, the inclined joining portion (3a2) extending by a welding portion (3a3) in longitudinal continuity with the peripheral edge of the first sheet, • wherein the longitudinal continuity is defined by a longitudinal alignment of at least part of a mid-thickness zone of the welding portion (3a3) with at least part of a mid-thickness zone of the peripheral edge of the first sheet, and • wherein the longitudinal alignment of the mid-thickness zones (6,7) is defined by the position on the edge (2a3) of the peripheral edge of the first sheet of a projection point of at least one straight line which is parallel to the mid-thickness surface zone of the second sheet and which is located in the corresponding mid-thickness zone, said position being located within the mid-thickness zone of the first sheet, • wherein each said mid-thickness zone (6,7) is defined in cross section by a zone (H 21,H 31) centred on the mid-thickness (6a,7a) of the corresponding sheet (2,3), having a thickness equal to 40% of the thickness of the respective sheets or. • wherein the longitudinal continuity is defined by a longitudinal alignment of at least part of a mid-thickness zone of the welding portion (3a3) with at least part of a mid-thickness zone of the peripheral edge of the first sheet, and • wherein the longitudinal alignment of the mid-thickness zones (6,7) is defined by the position on the edge (2a3) of the peripheral edge of the first sheet of a projection point of at least one straight line which is parallel to the mid-thickness surface zone of the second sheet and which is located in the corresponding mid-thickness zone, said position being located within the mid-thickness zone of the first sheet, • wherein each said mid-thickness zone (6,7) is defined in cross section by a zone (H 21,H 31) centred on the mid-thickness (6a,7a) of the corresponding sheet (2,3), having a thickness equal to 40% of the thickness of the respective sheets or. iv) welding the first and second steel sheets thus positioned by using a filler wire which is deposited in the groove previously made, wherein said welding wire, after melting and cooling, constitutes a weld bead connecting the first sheet to the second sheet and being part of said welded steel part, the end portion (3a1) of the peripheral edge of the second sheet being a welding support sheet,