采用热轧的方式制备了不锈钢/碳钢包层钢筋, 研究了包层钢筋的机械性能及界面的结合情况. 通过拉伸、剪切实验测试了钢筋的抗拉强度等性能及两金属的结合强度. 应用OM, SEM, EDS以及显微硬度仪对界面附近的显微形貌、元素扩散以及显微硬度分布进行分析. 实验结果显示:不锈钢/碳钢包层钢筋的轧制过程中双金属等比例延伸,其抗拉强度高达550 MPa, 延伸率45%, 拉伸过程中出现明显缩颈,断口处两金属未分离. 随轧制道次的增加, 金属结合更加致密, 剪切强度增加, 最大剪切强度为333 MPa, 剪切断裂面出现典型的塑性韧窝和剪切滑移. 界面附近出现了明显的元素扩散, 不锈钢中的Cr, Mn和Ni等元素向碳钢扩散, 碳钢中的Fe元素向不锈钢扩散,总扩散距离约30 μm, 造成界面附近碳钢侧的显微硬度显著增大,第6道次后其值为399.4 HV, 远高于碳钢基体的硬度.复合包层钢筋界面间形成了良好的冶金扩散结合.
Because of climate and human factors, the corrosion of reinforced steel bar has become 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 resistant 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. Then, 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. It makes the microhardness of the carbon steel near the interface increased significantly and the value is 399.4 HV which is higher than carbon steel after sixth pass rolling. Therefore, the metallurgical diffusion bonding is formed in the interface of clad bar.
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