Manufacturing of high strength bimetallic section steel with hot-rolling process

This study aimed to develop a 316L/35# stainless steel–bimetallic section steel to satisfy plasticity and strength standards. The stainless steel bimetallic section was made of 316L stainless steel, whereas the base metal was made of 35# carbon steel, rolled using 13 rolling mills at 1150 ​°C by applying interface vacuum technology. Moreover, the mechanical properties and microstructure of the composite interface of hot-rolled stainless steel–bimetallic section steel were analyzed at multiple scales. The finished, rolled-section steel was selected as the research object. Various experiments were conducted from multiple scales: transmission electron microscopy (TEM), electron probe micro-analyses (EPMA), and scanning electron microscopy (SEM) were utilized, among other techniques for testing the mechanical properties. The results revealed that distinct carburized and decarburized zones were formed on both sides of the composite interface due to the diffusion of elements. The width of the carburized zone was 30–50 ​μm, and the hardness was 184.3HV, whereas the width of the decarburized zone was 80–100 ​μm, and the hardness was 146.4HV. In the carburized zone, short, rod-like martensite, second-phase precipitates, and chromium carbide and oxides were observed. The shear strength of the stainless clad section steel was 384.62 ​MPa and the ultimate strength was 599.76 ​MPa, far exceeding the 210 ​MPa required in the standard, which revealed that the bimetal achieved good metallurgical bonding. This study serves as an important theoretical basis for conducting structural integrity evaluations of bimetallic materials.