Development of High-Strength and Atmospheric Corrosion Resistant Steel Bars with Low Cost

Some measurements including tensile test, cyclic immersion corrosion, metallographic microscopy, SEM and XRD were used to clarify the influence of Cu, P addition and cooling conditions on strength and corrosion resistance to explore low-cost, corrosion resistant and high-strength steel bars of Cu–P series. The addition of copper and phosphorus can effectively eliminate sulfide precipitation at grain boundaries and transform the sulfides inclusion in tensile fracture to oxides with higher strength, which is good for the strength of steel bars. Meanwhile, the rust layer of Cu–P series steel bar has better compactness and chemical stability, which favors to delay corrosion rate. Increasing the cooling rate refines the grain size and improves the microstructure, both of which are conducive to enhance the strength of steel bars. Therefore, low-cost Cu–P series HRB500aE steel bar can be developed by controlling composition and cooling rate. Compared with 20MnSi steel bar, Cu–P series steel bar reduces Mn content and avoids the addition of precious alloy elements such as Ni and Cr.