X15CrNiSi2520钢焊缝超高温服役失效分析

Failure Analysis on X15CrNiSi2520 Steel Welds in Superelevated Temperature Service

对X15CrNiSi2 52 0钢焊缝超高温服役前后的显微组织进行了观察分析 ,认为焊缝先于母材失效的主要原因是焊缝的服役温度过高 ,其次是Si含量偏低 ,焊缝中硅酸盐夹杂偏多 ,且不均匀 。

The microstructure of the welds of a rotary annealing furnace (ROF) inner cover made up of X15CrNiSi2520 steel and E2520R26 electrode before and after superelevated temperature service were observed and analyzed. In as welded joint, microstructure of the weld appeared as austenitic columnar crystal and inclusions. The inclusions superabounded and were not uniformed in weld. In serviced joint, a number of intermittent grooves appeared in weld that contacted with high temperature gases. A lot of circular Cr riched phase was showed in cross section of the weld in which grooves had generated. Inclusions were observed in partial weld. But Ni riched square was showed in boundary layer and Cr riched circle was showed in secondary layer in cross section of the weld in which groove was not generated. The Cr riched circle was discriminated as σ phase that was generated from austenitic heat resistance steel in super elevated temperature service and was harmful to high temperature strength. The Ni riched square was not discriminated, but it was beneficial to rising resistance to elevated temperature oxidation of weld. The data of electrodes in the Mill Test Certificate provided by the sapplier and results of composition of the weld measured by user both showed that Si content was lower than nominal content. It is pointed out that the primal failure reasons of the welds prior to the failure of base metal were as follows: ① The service temperature of weld was higher than permissive temperature. ② Si content in welds was lower than base metal. ③ The inclusions superabounded and were not uniformed. Hence, resistance to elevated temperature oxidation of the welds was lower than the base metal and was not uniformed.