Abstract: The disclosure relates to a multi-part mold for aluminothermic welding without preheating of metal parts, said mold having internally employed a welding cavity and two rising channels with variable cross-sections along their height, the central part of welding cavity being located below with respect to the lateral parts of welding cavity, said welding cavity having an increased moment of inertia of cross-section and an increased height from the lower side of base portion of welding cavity to the neutral axis of welding cavity, said rising channels extending from a region lower than said base portion, said welding cavity and said rising channels being connected together through two connecting ducts extending from the lower side of base portion to the head portion of welding cavity, the invention further relating to a process of reaching the metal parts by the liquid steel first underneath the lower side of base, a process of creating a liquid bath of constant height in an early stage of pouring operation and t