Insert intended for the assembly of a first part and a second part by electric resistance welding, and assembly method using this insert

An insert intended for the assembly of a first part and a second part by electric resistance welding of the insert and of the second part, wherein the insert comprises:

• a head portion, the head portion comprising a docking face configured to receive a welding electrode and a bearing surface configured to bear on the first part in order to hold the first part assembled to the second part,
• a body portion intended to be inserted into the first part, the body portion comprising a welding surface configured to be welded to the second part, the body portion having a section smaller than that of the head portion, and
• a thermal decoupling element extending around the body portion to prevent a transmission of the heat released by the body portion to the first part during a welding operation, wherein the thermal decoupling element comprises a peripheral groove containing a heat-insulating material, the peripheral groove is delimited by one element or several elements projecting from an underside of the head portion, and wherein the insert comprises a holding element configured to hold the insert in position through the first part, the holding element comprising an outer side face of the one element or the several elements projecting from the underside of the head portion intended to keep the body portion at a distance from the first part when the insert is integrated with this first part, and wherein the peripheral groove is configured to serve as a receiving area for splashes of melting matter during the welding operation, said splashes being blocked by the one element or several elements projecting from an underside of the head portion.