Q235B环形铸坯显微组织和力学性能的研究

Study on the Microstructure and Mechanical Properties of Q235B Ring Casting Blank

针对短流程铸辗复合成形工艺,以法兰常用材料Q235B碳素钢作为研究对象,通过金相观察、力学性能测试和断口扫描等试验,研究砂型铸造方式和离心铸造方式对环形铸坯组织和力学性能的影响。结果表明,Q235B碳素钢的室温组织主要由铁素体和珠光体组成;砂型铸坯中的铁素体以块状的形式存在,且晶粒较为粗大,离心铸坯中的铁素体以针状和块状的形式存在,且晶粒较为细小。离心铸坯的抗拉强度和塑性、冲击韧度均明显优于砂型铸坯。砂型铸坯的拉伸断口呈现韧窝和准解理并存的混合断裂特征,冲击断口几乎为完全的脆性解理断裂特征;离心铸坯的拉伸断口几乎为完全的韧性断裂特征,冲击断口由撕裂韧窝区域和解理区域组成。

Aiming at cast-rolling forming technology, by means of metallographic observation, mechanical properties test and fracture observation, the effect of different casting methods （sand casting and centrifugal casting） on the microstructure and the mechanical properties of the Q235B carbon steel are investigated. The results show that the microstructure of Q235B carbon steel at room temperature is mainly composed of ferrite and pearlite. The ferrite in the sand casting blank exists in the form of massive, and the grains are coarse. The ferrite in the centrifugal casting blank exists in the form of needle and massive, and the grains are small. The tensile strength, plasticity and impact toughness of the centrifugal mold casting blank are significantly better than that of sand casting blank. The tensile fracture of sand casting blank is a mixed fracture characteristics of quasi-cleavage and dimple. The impact fracture is almost completely brittle cleavage fracture characteristics. Centrifugal casting tensile fracture is almost entirely ductile fracture characteristics, and the impact fracture is composed mainly of tearing dimple and cleavage region.