Method and hot-forming die for producing a heat transfer plate

A method for producing a heat transfer plate with the following steps:

• Providing a plate stack which is constituted from at least two plate elements made from a metal material with a brazing material arranged between the plate elements;
• Transferring the plate stack into a heated hot-forming die which has a lower die and an upper die and contact surfaces with at least one duct cavity;
• Placing the plate stack inside the hot-forming die, wherein the plate stack is positioned on spacer elements which are arranged so that they can flex in the lower die and project relative to the contact surface of the lower die;
• Closing the hot-forming die, wherein the lower die and the upper die are displaced relative to each other;
• Continuing the closing movement and clamping the plate stack between the lower die and the upper die, wherein the spacer elements in the lower die are displaced into the lower die and the plate stack comes into surface contact with the lower die and the upper die;
• Heating the plate stack;
• and
• Applying an internal pressure to an intermediate space between the plate elements of the plate stack by feeding in an active medium and forming a duct by deforming, using internal pressure, at least one plate element region into the duct cavity, the duct cavity being vented, and
• Melting the brazing material between the plate elements and joining by brazing the plate elements at joining surfaces of the plate elements which bear against one another;
• Opening the hot-forming die, wherein the lower die and the upper die are displaced relative to each other, wherein the spacer elements in the lower die are moved out from the lower die such that the plate stack is held on the spacer elements in the lower die with a spacing from the lower die;
• Holding and cooling the plate stack;
• Opening the hot-forming die until it is in a removal position (E) and removing the heat transfer plate from the hot-forming die.