Hot Formed Tank Heads

For hot-formed tank heads made of stainless steel, copper, nickel, and nickel alloys, electric furnaces are recommended for heating. Gas or fuel furnaces may also be used; however, charcoal or coal-fired furnaces should not be used.

The reasons for Dalian Dingjin to perform heat treatment  necessarily and strictly on hot-formed tank heads are explained below for your reference.

During the heating and cooling processes, stainless steel dished heads experience uneven thermal expansion and contraction due to differences in cooling rates and durations between the surface and the interior. This results in the generation of thermal stress.

Since the surface temperature is lower than that of the interior, the surface contracts more than the interior under internal stress. After complete cooling, the interior cannot contract freely, which causes compressive stress on the surface and tensile stress within the interior. This phenomenon is mainly influenced by factors such as cooling rate, material composition, and the heat treatment process.

As the cooling speed increases and with higher carbon content or alloying elements, the uneven plastic deformation caused by thermal stress becomes more pronounced, leading to greater residual stress. Additionally, during the heat treatment of stainless steel sheets, structural transformations occur-such as the transformation of martensite into austenite-which causes volume expansion due to increased specific volume. This leads to inconsistent volume changes across different parts of the workpiece and results in the generation of structural stress.

This structural stress typically manifests as tensile stress on the surface and compressive stress at the center of the stainless steel head, which is the opposite of thermal stress. The magnitude of structural stress depends on factors such as cooling rate, geometry, and material composition within the austenitic transformation zone.

However, internal stress in stainless steel heads is already present before any structural transformation takes place. Structural stress arises during the transformation process, and throughout the entire cooling phase, the combined effects of both internal and structural stresses determine the actual stress state within the workpiece. This combined stress is complex and influenced by various factors, including material composition, shape, and the specifics of the heat treatment method.

Dalian Dingjin never compromises on the quality of hot-formed tank heads, even if it means losing opportunities to support more clients. Sometimes, we receive feedback from potential clients saying that our prices are higher than those of other competitors. However, as everyone knows, quality determines price. Therefore, our team confidently assures you that the hot-formed tank heads manufactured by Dalian Dingjin are made from qualified raw materials and meet high-quality standards.