Q690NHH耐蚀耐火钢HAZ过热区组织为马氏体和贝氏体的混合组织，随t_8/5增加，过热区组织中马氏体数量逐渐减少，贝氏体组织数量逐渐增加，硬度逐渐下降；当t_8/5=1.7s时，过热区组织为40%M+60%B，当t_8/5=9.3s时，过热区组织为10%M+90%B，硬度HV5 为273。当23.2s≤t_8/5<730s区间时，HAZ过热区组织为100%贝氏体,硬度HV5在210以上。当t_8/5≥810s时，HAZ过热区组织为贝氏体、铁素体和珠光体混合组织，随t_8/5增加，硬度略有降低，但变化不大。

Q690NHH corrosion-resistant fire-resistant steel HAZ superheated zone structure is a mixed structure of martensite and bainite. With the increase of t8/5, the number of martensite in the superheated zone structure gradually decreases, the number of bainite structure gradually increases, and the hardness gradually decreases; When t8/5=1.7s, the superheat zone organization is 40%M+60%B, when t8/5=9.3s, the superheat zone organization is 10%M+90%B, and the hardness HV5 is 273. When 23.2s≤t8/5<730s, the HAZ superheated zone structure is 100% bainite, and the hardness HV5 is above 210. When t8/5≥810s, the HAZ superheated zone structure is a mixed structure of bainite, ferrite and pearlite. With the increase of t8/5, the hardness decreases slightly, but the change is not significant.