MICROSTRUCTURE TRANSFORMATION IN THE WELDING HEAT AFFECTED ZONE OF 800MPa GRADE ULTRA FINE STRUCTURED STEEL

The transformation behavior and microstructure development in the heat affected zone(HAZ) of 800MPa grade ultra fine structured steel was investigated. It was found thatthe HAZ has intermediate temperature transformation characteristics in a wide rangeof cooling rates, with the bainite sheaves consisting of bainite ferrite plates withoutcarbide precipitation and retained austenite in the fast cooling regime. At relativelyhigh cooling rates, which corresponded to low heat inputs, the hardness of the simulatedHAZ was above that of the base metal. When the cooling rate was below 9℃/s, thewelding HAZ would have an obvious softening. The analysis of transformation ratesin continuous cooling processes was completed by numerical differential method. Theresult indicated that the microstructure transformation rate of the HAZ in 800MPagrade ultra fine structured steel changed sharply to slow speeds when the cooling timet_(8/5) is longer than 7s.

新加坡总体规划情况下结核病化学治疗的肝毒性反应

背景:新加坡结核病控制中心——一个大规模的国家结核病人诊治中心。 目的:观察抗结核药物诱导性肝炎(DH)的发病率、临床经过、结局及在总体规划条件下与DH有关的危险因素。 设计:对1998年抗结核治疗的成年病人回顾性分析。 结果:1998年治疗的1036例病人中,共发生DH 55例。DH诊断的中位时间为38天。与DH显著有关的因素是基线转氨酶/胆红素异常(OR 2.1,95％CI1.1-4.3,P=0.02),>60岁(OR 1.97,95％CI1.14-3.34,P=0.01)及女性(OR 1.9,95％CI1.07-3.4,P=0.02)。而人种、自报的不同的饮酒量及体重均与叫发生无关。3例致死性肝炎均接受含PZA的方案。48例重新开始治疗者中45例完成治疗。再次建立结核治疗的中位时间为23天。 结论:抗结核药物诱导性肝炎的发生率为5.3％。与DH发生有关的危险因素为>60岁、基线转氨酶/胆红素异常及女性。