深海浮体用R6级系泊长链的热处理

Heat Treatment of R6 Grade Offshore Mooring Long Chains Used for Deep Sea Float

在立式连续炉中以0.08~0.24 m/min的线速度对直径92 mm、控制和未控制含氮量的复合贝氏体钢制深海系泊长链分别进行了不同工艺的热处理:经930℃和880℃两次水淬随后高温回火、经980℃水淬随后高温回火和普通的920℃水淬和高温回火热处理后,检测了链环的力学性能、奥氏体晶粒度和碳含量分布。结果表明:与经两次淬火随后回火的控氮复合贝氏体钢链环相比,经980℃淬火、回火的链环的晶粒更为细小、强韧性更好,焊缝碳含量的均匀性提高了1个数量级。此外,在连续炉中980℃淬火和回火的处理周期不仅可缩短半年以上,还能使系泊链达到R6级的强韧性水平及优良的在海洋环境中的抗开裂性能。

Deep sea offshore mooring long chains 92 mm in diameter,made of composite bainnitic steels in which nitrogen content was and did not be controlled,were respectively heat treated at linear speeds of 0.08 to 0.24 m per min in a continuous heat treatment furnace:two separate water-quenching from 930 ℃ and 880 ℃ and then high tempering,water-quenching from 980 ℃and then high tempering,and conventional water-quenching from 920℃ and then high tempering.After this,the links were tested for mechanical properties,austenite grain size and distribution of carbon content.The results showed that the link made of composite bainitic steel controlling nitrogen content quenched from 980 ℃then tempered exhibited finer grains and better both strength and toughness,and one order of magnitude higher uniformity of carbon content in weld,as compared with those of the link double quenched then tempered.In addition,the quenching from 980 ℃ and tempering in the continuous furnace can not only shorten the heat treatment cycle by more than half a year but also enable the offshore mooring chain to achieve R6-grade of strength and toughness and to offer excellent resistance to cracking in marine environment.