轧制加热温度对钛/钢复合板组织与性能的影响

Effect of heating temperature on microstructure and mechanical properties of titanium clad steel by hot roll bonding

摘要:

采用钢/钛/隔离剂/钛/钢对称结构复合板坯,研究了轧制加热温度(850-1000℃)对钛/钢复合板显微组织、基材强韧性和界面结合性能的影响。结果表明,随着轧制加热温度的升高,界面剪切性能逐步下降。加热温度影响着界面反应相的种类和厚度。在850,875,900℃条件下,轧后冷却扩散过程中,C极容易在钛/钢界面形成TiC层,阻碍了Fe向Ti中扩散,因而界面形成TiC和β-Ti反应层；在950℃和1000℃条件下,由于C在β-Ti中的扩散系数为C在γ-Fe扩散系数的10倍以上,C不能在结合界面富集形成有效的TiC屏障,此时Fe能够在Ti中充分扩散,从而形成了Fe-Ti金属间化物层、TiC层、β-Ti层和α-β Ti层。脆性反应相的厚度与加热温度呈正相关关系。脆性相种类和厚度增加使得钛/钢复合板界面剪切强度出现下降。

Abstract:

A symmetry assembled slab of steel/titanium/separating agent/titanium/steel was designed for fabricating titanium clad steel by hot roll bonding. Effect of heating temperature on microstructure, strength-toughness and bonding properties of clad steel plates were investigated at condition of 850-1000℃. The results show that with the increase of temperature, the shear strength decreases obviously. The heating temperature has an important effect on the variety and thickness of interfacial phase. At temperature of 850, 875 and 900℃, carbon can easily diffuse to the bonding interface to form the TiC layer at the cooling process of roll bonding. The TiC plays an role of barrier to hinder the diffusion of iron into titanium. Consequently, TiC and β-Ti are formed at the Ti/steel interface. While at temperature of 950 and 1000℃, carbon can not enrich at the Fe/Ti interface owing to that the diffusion coefficient of C in β-Ti is over 10 times bigger than that of C in γ-Fe. Therefore, iron can diffuse sufficiently into titanium to form the interface products consisted of Fe-Ti intermetallic compounds, TiC, β-Ti and α-β Ti. In addition, the increase of heating temperature promotes the rise of brittle phase layer thickness. The reduction of shear strength is attributed to the increase of variety and thickness of brittle phase.