EFFECT OF MULTIPASS HOT ROLLING ON THE PROPERTY AND BONDING INTERFACE OF CLAD BAR

Abstract

Because of climate and human factors, the corrosion of reinforced steel bar has be- come one of the important reasons of premature deterioration of concrete buildings and infrastructure. Stainless steel bar cannot be widely used due to its high price. Therefore, stainless steel clad carbon steel bar comes into being. It is a new material used in construction, which is made up of corrosion re- sistant stainless steel outer layer and carbon steel core. In the present study, an experimental study was conducted to investigate the mechanical property and bonding state of stainless steel clad carbon steel bar. The tensile strength of clad bar and bonding strength of two metals were measured using tension test and shearing test. Further, microscopic morphology, element diffusion and microhardness near the interface were analyzed using OM, SEM, EDS and microhardness tester. The results show that the two metals of the bar extend proportionally in the rolling process. The tensile strength is 550 MPa and the percentage of elongation is 45%. The neck phenomenon in the tensile experiment is obvious and the two metals are undivided in the fracture. With the increment of rolling pass, the bonding between the metals becomes denser and this increases the shearing strength. The max shearing strength is 333 MPa and the typical plastic dimples and shearing slip were observed on the shearing fracture surface. Element diffusion occurs at the interface where the Cr, Mn, Ni of stainless steel diffuse into carbon steel and the Fe of carbon steel diffuses into stainless steel, and the total width of diffusion distance is about 30 μm. After sixth pass rolling the microhardness of the carbon steel near the inter- face increased significantly to 399.4 HV which is higher than carbon steel. The metallurgical diffusion bonding is formed in the interface of clad bar.