Abstract
Three low‐carbon bainitic steels were designed to investigate the effects of Cr and Al addition on bainitic transformation, microstructures, and properties by metallographic method and dilatometry. The results show that compared with the base steel without Cr and Al addition, only Cr addition is effective for improving the strength of low‐carbon bainitic steel by increasing the amount of bainite. However, compared with the base steel, combined addition of Cr and Al has no significant effect on bainitic transformation and properties. In Cr‐bearing steel, Al addition accelerates initial bainitic transformation, but meanwhile reduces the final amount of bainitic transformation due to the formation of a high‐temperature transformation product such as ferrite. Consequently, the composite strengthening effect of Cr and Al addition is not effective compared with individual addition of Cr in low‐carbon bainitic steels. Therefore, in contrast to high‐carbon steels, bainitic transformation in Cr‐bearing low‐carbon bainitic steels can be finished in a short time, and Al should not be added because Al addition would result in lower mechanical properties.
Highlights
Low-carbon bainitic steels are commonly designed with alloying elements added to achieve favorable properties [1,2,3,4,5,6,7,8,9,10,11]
The grain sizes of prior-austenite before heating treatment are measured by Image-Pro Plus software to be sizes of prior‐austenite before heating treatment are measured by Image‐Pro Plus software to be
Metallographic method and dilatometry were used to investigate the effects of Cr and Al addition on bainitic transformation, microstructures, and properties
Summary
Low-carbon bainitic steels are commonly designed with alloying elements added to achieve favorable properties [1,2,3,4,5,6,7,8,9,10,11]. It is well known that the mechanical properties of bainitic steel are significantly influenced by the volume fraction of bainite, the amount of retained austenite (RA), the precipitation of cementite, among other factors [2]. The main purpose of the addition of alloying elements is to promote bainitic transformation and control the microstructures. A higher strength can be achieved due to precipitation hardening and grain refinement effects by adding vanadium, titanium, molybdenum, or niobium [7,8,9,10,11]
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