There are a variety of low carbon steel parts for mechanical purposes, the actual application process requires a high mechanical property. However, in the actual production, we often find the presence of low-carbon steel parts banded structure after thermal processing. Such as the banded structure is steel in a defect organization, when serious band structure, the mechanical properties of steel apparent anisotropy, the steel pipe to reduce the transverse section shrinkage more vertical and horizontal impact energy about the difference double, plastic or steel toughness not meet the technical requirements of the standard.

Reasons for the formation of low carbon steel banded structure

In the carbon content of 0.10% ~ 0.35% of the low carbon steel smelting pouring in after the majority to go through plastic deformation (rolling, forging, thermal expansion), before becoming profiles. However, after processing of low carbon steel parts easy to get along the deformation direction, forming pearlite and ferrite lanes zonal distribution, namely the formation of banded structure. Reasons for the formation of low carbon steel parts banded structure vary, summed up roughly two kinds of reasons:

(1) caused by the segregation of the band structure, that is, when the inclusion of low-carbon steel parts contain a certain amount of time rolling inclusions along the rolling direction away streamline distribution. When cooled to a low-carbon steel parts Ar3 below, these impurities became eutectoid ferrite core nucleation make eutectoid ferrite inclusions around the first generation of zonal distribution form, then the residual austenite body into pearlite, observed under microscope at room temperature, ferrite is white, grayish-black and pearlite, resulting in white and black stripes, which is a low-carbon steel strip tissue deformation.

(2) the band structure by thermal processing temperature caused by improper, that the thermal processing of low carbon steel parts to stop forging temperature at the time of the two-phase zone (between A1 and A3), ferrite along the flow direction of the metal from the austenite zonal precipitation, decomposition of the austenite is not yet cut into strip when cooled to A1, the strip austenite into pearlite band.