采用经过改进的核反应产物粒子径迹照相技术,研究25MnTiBR钢中硼的分布状态及其对钢的淬透性的影响。试验结果表明,硼的平衡偏聚在高温奥氏体化时消失;硼钢在淬火过程中产生的晶界偏聚是一个非平衡的动力学过程。随奥氏体化后,淬火温度升高使偏聚程度增加,以及在其附近出现贫硼区,是晶界非平衡偏聚的显著特征。 在25MnTiBR钢中加入0.4％稀土金属,在一定温度范围内有显著阻碍硼向奥氏体晶界偏聚的作用。这可能主要是由于稀土元素在此温度范围内存在有平衡偏聚的结果;硼和稀土元素在奥氏体晶界偏聚,以一定程度互相配合,对提高钢的淬透性是有利的。
The distribution of boron and its effect on the hardenability of a 25Mn-TiBR steel have been investigated by means of modified particle-tracking auto-radiography. The results indicate that boron exists in the forms of equilibrium andnon-equilibrium segregation along grain boundaries. The equilibrium segrega-tion of boron disappeared during high temperature austenization. The non-equi-librium segregation along grain boundaries of a quenched boron steel occurredduring cooling by diffusion from their neighbouring regions. The degree of segre-gation increased and a boron depleted-zone appeared next to the boundaries asthe austenizing temperature was raised. The effect of rare earth additives on the distribution of boron in 25MnTiBRsteel has also been investigated. It was found that within a certain temperaturerange the segregation of boron to austenite grain boundaries was hindered bythe addition of 0.4％ mischmetal. This was possibly caused by an equilibriumsegregation of rare earth elements along the austenite grain boundaries. It hasbeen confirmed that the simultaneous addition of boron and rare earth mischme-tal further increases the hardenability of the steel. Suggestions have been maderelating to the possible mechanism of this effect.
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