Nb含量对制氢转化炉管HP合金组织转变规律影响的研究

离心铸造的HP40和HP40-Nb合金被广泛用作制氢转化炉炉管材料,通常管壁温度可高达1000℃。通过观察HP40和HP40-Nb合金在原始铸态和高温状态下的显微组织,研究了不同Nb含量对合金共晶组织稳定性的影响。采用扫描电镜和X射线衍射仪研究了炉管材料的显微组织和相结构。研究结果表明:在碳含量0.4%左右的HP合金中,Nb含量0.210%~0.357%时主要起到固溶强化作用,共晶碳化物主要是M7C3,仅有少量的富Nb共晶MC散布在晶界上;当Nb含量0.89%~1.55%时,HP40-Nb原始铸态组织中析出了富Cr的M7C3碳化物和富Nb共晶MC。对于高温状态下的HP40-Nb合金,在晶界和枝晶间形成的富Nb共晶的MC提高了原始共晶组织的稳定性,使得炉管材料的使用温度可向高温推移。

Effects of Niobium on the Microstructure Evolution of HP Alloys Used in Hydrogen Generation Tube

The HP40 and HP40 -Nb alloys made by centrifugal casting are widely used in the material of the reformer in hydrogen generation tube, the temperature at the surface of the tube reached up to 1000 ℃. By observing of the microstructure of as -casted, tempered and served HP40 and HP40 -Nb tubes, the effect of Nb concentration on the stability of the eutectic structure was studied. The microstructure of the tube was researched by scanning electron microscopy （ SEM ） and X - ray diffractometer （ XRD ）. The result indicated that in the HP alloy in which Carbon content was about 0.4%, the Nb content at the range of 0.210% to 0. 357%, the Nb played a major role in solution strengthening, the euteetic carbide was M7C3, only a little Ni -riched eutectic MC diffused in the grain boundaries. When the Nb content was ranged from 0.89% to 1. 55% , the Cr- riched M7C3 and Nb -riched eutectic MC were isolated the HP40 -Nb as- cast structure. When the HP40 -Nb alloy worked at high temperature, the Nb -riched eutectic MC which was formed around the grain boundaries and the dendrites facilitate the using tempera- ture of the tube material to higher temperatures.