影响E级船板钢无塑性转变温度因素的探讨

Discussion on the Factors Influencing the NDT Temperature of Hull Structural Steel Plates of Grade E

E级系列船板钢主要难点是无塑性转变温度(NDT)较难保证合格,以致生产的钢材整批判废。对NDT试验后的试样进行化学成分、金相组织、夹杂物等分析,找到影响NDT温度的因素,并对工艺进行了优化。经过试验分析,要得到无塑性转变温度低于-40℃,应采取以下措施:用Δ=0.5(V+Al)+Nb+Ti值、(Cu+As)值控制合金元素,Δ值应在0.065%~0.090%,(Cu+As)值应<0.060%;夹杂物控制在1.5级以下,带状组织控制在3.0级以上,晶粒度控制在9.0级以上,铁素体含量控制在60%~80%;生产过程尽量采用正火工艺,E级系列船钢板终轧温度按790±20℃控制,钢板的开轧温度应确保在1 070~1 120℃,具体控制目标按1 080±10℃控制。

The main difficulty of hull structural steel plates of Grade E series is that it is difficult to ensure the conformity of NDT temperature,which leads to the complete waste of steel produced.The chemical composition,metallographic structure and inclusions of the samples are analyzed after NDT test in order to find out the factors affecting the NDT temperature,optimize the process,and get the products with qualified NDT temperature.After experimental analysis,the following measures should be taken to obtain that the NDT temperature is lower than-40℃:useΔ=0.5(V+Al)+Nb+Ti value,(Cu+As)value to control alloy elements,the value ofΔis in the range of 0.0650%-0.090%,and the value of Cu+As is in the range of<0.060%,which is a necessary condition;The inclusions are controlled below grade 1.5,the banded structure is controlled above grade 3.0,the grain size is controlled above grade 9.0,and the ferrite content is controlled between 60% and 80%;Normalizing process shall be adopted as far as possible in the production process.The final rolling temperature of hull structural steel plates of Grade E series shall be controlled at 790±20℃,and the starting rolling temperature of steel plate shall be ensured at 1070~1120℃,and the specific control target shall be controlled at 1080±10℃.