When the content of hydrogen in the casting reaches a certain value, its mechanical properties will be severely reduced, and even hydrogen embrittlement will occur, causing the casting to be scrapped.
From the analysis of the source of hydrogen in castings, the sources of hydrogen in steel can be divided into "internal" and "foreign". The former refers to the hydrogen absorbed by the steel during the smelting process and the subsequent processing and manufacturing processes. The other is the hydrogen contained in steel in the service environment. Since the produced castings have not been processed and manufactured, and there is no problem with service environmental media, the source of hydrogen in steel parts can only be generated during the smelting process. According to this situation, a dehydrogenation heat treatment process for different materials is formulated
Process principles
The principle of dehydrogenation heat treatment process is:
(1) Because hydrogen is distributed in steel in atomic or molecular state, only by adopting the theory of molecular thermal kinematics and formulating reasonable heating, heat preservation and cooling methods, can the hydrogen in the steel diffuse to the surface of the steel to achieve the purpose of hydrogen removal.
(2) Since stainless steel and ferritic steel containing more than 13% chromium are heated to 475 ° C, the strength of the steel is accompanied by the phenomenon of brittleness, so the dehydrogenation temperature is preferably higher than 475 ° C .