熔速对氩气保护GH4169G合金电渣锭组织及夹杂物的影响

研究了熔速对氩气保护GH4169G电渣锭宏微观组织及非金属夹杂物的影响。结果表明:适当增加熔速有利于缩短铸锭的局部凝固时间，减小二次枝晶间距，从而细化枝晶组织，但对Nb、Ti等易偏析元素沿径向的宏观分布影响不大。熔速对GH4169G铸锭中的夹杂物类型影响较小，主要为氧化物、氟化物和氮化物三类。夹杂物在铸锭表面最多，向内部迅速减少并趋于稳态。铸锭内部夹杂物多以氧化物为核心，氮化物为次外层，碳化物为最外层的双层或三层结构。采用MeltFlow-ESR模拟方法，分析了熔速对重熔过程中夹杂物运动轨迹的影响，发现提高熔速有利于夹杂物向铸锭表面运动，降低铸锭表面夹杂物富集区的厚度和铸锭内部夹杂物的数量。此外，提高熔速有利于缩短夹杂物析出长大的时间，降低夹杂物尺寸。

Effect of Melting Rate on Structure and Inclusions of GH4169G Alloy Ingot Fabricated by Argon Protected Electroslag Melting

Electroslag remelting (ESR) has been widely applied as an important technology to produce ingots for special steels and alloys because of its remarkably advantages, such as the process can purify the prepared ingots by effectively eliminating the impurity sulfur and the large inclusions. However, as one of the most important parameters of ESR, the effect of melting rate on the purity of ingot is still controversial. For this purpose, the macro- and micro-structure and nonmetallic inclusion characteristics at different positions of GH4169G ingots produced by industrial-scale argon protected electroslag remelting (PESR) technology with 2 remelting rates were comparatively investigated by means of OM, SEM, EDS and EPMA. The results indicate that a proper high melting rate is beneficial to shorten the local solidification time of ingot, reduce the secondary dendrite arm spacing and refine dendrite structure, but has little effect on the distribution of Nb, Ti and other elements along the radial direction in macro-scale. Besides, the melting rate has little effect on the inclusion types of GH4169G ingot, which are mainly oxides, fluorides and nitrides. The inclusions in the ingot are usually double or three layers with oxide as the core, nitride as the secondary outer layer and carbide as the outermost layer. The influence of the melting rate on the movement of inclusions in the remelting process was simulated via the so called MeltFlow-ESR software. It was found that the increase of melting rate was conducive to the movement of inclusions to the ingot surface, thereby the thickness of the inclusion enriched area on the surface of the ingot and the number of inclusions in the ingot could be reduced. In addition, the increase of melting rate can shorten the time of inclusion precipitation and reduce the size of inclusions.