Injection chamber that is applicable to be incorporated in machines for pressure die casting of hot non-ferrous materials and consisting in a cylinder formed from an assembly that comprises an external envelope and an internal insert through which the material is passed under pressure through an opening and pushed by means of a piston from one end of the cylinder to inside a mold located at the opposite end, the external diameter (d) of the internal insert is smaller than the internal diameter of the external envelope, between both diameters (d, D) a difference of size (a) existing so that it allows the introduction and extraction of the said insert in the envelope directly and cold, that means, without expanding it, and that the sole expansion the said insert sustains, is the expansion formed by the heat of the material to be injected which passes through it when the cylinder is operating, reduces to zero the said difference of size (a) provoking its fixation within the envelope, where the envelope comprises a cooling system that comprises two areas configured to have a different degree of cooling; a first cooling area where the cooled area is limited to the lower part of the envelope, that means the part opposite to the opening; and a second cooling area located close to the mold where the cooled part comprises cooling the full circumference of the envelope characterized in that it possesses grooves in the insert for radially inserting retaining parts that are fixed to it with screws, acting as stop in the envelope, where the grooves are recesses of the external surface of the end of the insert, in small stretches that protrude externally to the envelope, and the retaining parts are formed by both sectors of circumference that are adjusted to the said grooves remaining coupled on the rim of the envelope, on which surface screwed holes have been pierced coincident with boreholes provided in the said parts for the passage of the screws, and further where the retaining parts possess protrusions that are introduced in slots of the insert preventing the rotation between the insert and the envelope. applicable to be incorporated in machines for pressure die casting of hot non-ferrous materials and consisting in a cylinder formed from an assembly that comprises an external envelope and an internal insert through which the material is passed under pressure through an opening and pushed by means of a piston from one end of the cylinder to inside a mold located at the opposite end, the external diameter (d) of the internal insert is smaller than the internal diameter of the external envelope, between both diameters (d, D) a difference of size (a) existing so that it allows the introduction and extraction of the said insert in the envelope directly and cold, that means, without expanding it, and that the sole expansion the said insert sustains, is the expansion formed by the heat of the material to be injected which passes through it when the cylinder is operating, reduces to zero the said difference of size (a) provoking its fixation within the envelope, where the envelope comprises a cooling system that comprises two areas configured to have a different degree of cooling; a first cooling area where the cooled area is limited to the lower part of the envelope, that means the part opposite to the opening; and a second cooling area located close to the mold where the cooled part comprises cooling the full circumference of the envelope characterized in that it possesses grooves in the insert for radially inserting retaining parts that are fixed to it with screws, acting as stop in the envelope, where the grooves are recesses of the external surface of the end of the insert, in small stretches that protrude externally to the envelope, and the retaining parts are formed by both sectors of circumference that are adjusted to the said grooves remaining coupled on the rim of the envelope, on which surface screwed holes have been pierced coincident with boreholes provided in the said parts for the passage of the screws, and further where the retaining parts possess protrusions that are introduced in slots of the insert preventing the rotation between the insert and the envelope.