Thermal shock while hot working special steels

What is Thermal Shock?

Thermal shock refers to the stress and potential damage, such as cracking. This occurs when a material undergoes a sudden and significant temperature change, resulting in a steep temperature gradient across its cross-section.

What are the main factors causing this?

One of the primary factors behind this phenomenon can be rapidly heating cold steel in a furnace. When cold steel is introduced to a hot furnace, the surface expands faster than the core, forming internal stress. On the opposite spectrum, rapid cooling can also shock the steel.

Uneven heating in the furnace may also contribute to this. Similarly, multiple hot working cycles without proper reheating methods may cause thermal shock.

Why are special alloys more prone to this?

Special steels contain exotic alloying elements that may have low thermal conductivity, high thermal expansion coefficient, and brittleness at forging temperature. All of these make steel highly susceptible to thermal shock. Therefore, forging precautions must be maintained based on the type of steel.

How to avoid thermal shocks?