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利用Gleeble-3500型热模拟试验机,进行NM450在不同热循环条件下的焊接热模拟试验,研究了t8/5对焊接热影响区粗晶区组织及性能的影响。结果表明:一次热循环t8/5从5 s增加到20 s时,粗晶区硬度逐渐下降,而冲击吸收功(-20℃)先增加后下降;当t8/5为15 s时,粗晶区冲击吸收功最高(46 J),冲击断口为准解理和微孔聚集混合型断裂,这是由于形成了板条马氏体和针状下贝氏体的混合组织,且马氏体发生了自回火。此钢种进行单道次焊接时,t8/5应控制在15 s左右。
Using the Gleeble-3500 thermal simulation testing machine, the thermal simulation test of NM450 under different thermal cycling conditions was carried out. The effect of t8 / 5 on the microstructure and properties of the HAZ was studied. The results show that the hardness of the coarse grain decreases gradually when the thermal cycle t8 / 5 increases from 5 s to 20 s, while the impact absorption energy (-20 ℃) first increases and then decreases; when t8 / 5 is 15 s, the coarse grain The zone has the highest impact absorption (46 J). The impact fracture is a quasi-cleavage and micropore aggregation mixed fracture, which is due to the formation of mixed martensite and acicular bainite and martensite Self tempering. This single-pass welding steel, t8 / 5 should be controlled at about 15s.