Analysis of stress magnitude
Thread Content
In chemical production, during the processes of heating and pressurization, we operate strictly in accordance with the specified rate of pressure increase; generally, we keep this rate at 0.1 MA per minute. I would like to ask everyone: if you try to destroy a container using external force under normal conditions, it’s very difficult to do so even with significant force. However, when such a device is exposed to high temperatures and then cooled suddenly, it can crack. We generally consider temperature changes as variations in stress, as well as internal compression of the metal atoms. Why does this result in such large forces? In my opinion, it is the forces between the atoms within it; under normal conditions these forces are relatively evenly distributed, but when an external force is applied, these forces become concentrated, resulting in high stress. Yet why does it possess such great internal strength?
Rapid cooling is very harmful; as the temperature drops, the brittleness of materials increases, and hydrogen embrittlement is likely to occur, especially in a hydrogen-rich environment. In high-temperature, high-pressure environments with hydrogen present, it is necessary to reduce the pressure first before cooling slowly.
The overall thermal stress is a type of secondary stress; rapid cooling can create significant temperature differences across different parts that are under constraints, leading to local plastic deformation. The accumulation of such irreversible deformation can result in cracks in those areas, ultimately causing the equipment to fail.