基于GBDT算法的Fe-36Ni/304L搭接接头特征尺寸及性能预测

Prediction of Feature Size and Performance of Fe-36Ni/304L Lap Joint Based on GBDT Algorithm

Fe-36Ni合金和304L奥氏体不锈钢是制备新一代液化天然气(LNG)船液舱围护系统的主要材料,由这两种材料焊接而成的复合结构是组成液舱围护系统的重要部分,因此研究Fe-36Ni/304L异种合金的焊接工艺及接头特征尺寸和力学性能预测具有重要意义.开展了Fe-36Ni/304L异种合金搭接脉冲钨极惰性气体保护焊(GTAW)立焊工艺研究,探索了脉冲焊接参数对接头宏观成形与拉伸性能的影响规律.根据Fe-36Ni和304L异种合金薄板搭接的脉冲GTAW试验结果,研究了焊接参数(峰值电流、基值电流、占空比、脉冲频率和焊接速度)与接头特征尺寸L(下板焊缝宽度)、P(下板焊缝熔深)、R(焊缝根部到焊缝表面的最短距离,即最小熔合半径)及拉伸最大承载力的关系.建立了基于梯度提升决策树(GBDT)算法的接头特征尺寸及性能预测模型,并研究了各焊接参数对特征尺寸和力学性能的影响程度.结果表明:Fe-36Ni/304L异种合金搭接脉冲GTAW立焊接头特征尺寸L和P主要与峰值电流、占空比和焊接速度相关,随着峰值电流和占空比的增加,L和P也随之增加;随着焊接速度降低,L和P随之增加.特征尺寸R主要与占空比和脉冲频率相关,随着脉冲频率和占空比的增加,R也随之增加.特征尺寸R是影响搭接接头拉伸最大承载力的主要因素,搭接接头的拉伸最大承载力可达12.66 kN.所建立的预测模型对特征尺寸和最大承载力的预测相对误差均在3%以内,模型的预测精度较高,且泛化性较好.

Fe-36Ni alloy and 304L austenitic stainless steel are the main materials for the manufacture of the new generation of liquefied natural gas(LNG)ship tank containment system.A composite structure fabricated using Fe-36Ni/304L dissimilar alloys is an important part of the tank enclosure system.Therefore,it is of great significance to conduct a study on the welding process and prediction of the feature size and mechanical properties of Fe-36Ni/304L dissimilar alloys.Aiming at the pulsed gas tungsten arc welding(GTAW)of Fe-36Ni/304L dissimilar alloys in a verti-cal welding position,this work investigated the influence of pulsed GTAW welding processes on the macroscopic formation and tensile properties of the welded joints.According to experimental results,the relationships between the welding parameters(i.e.,peak current,base current,duty cycle,pulse frequency,and welding speed)and the feature sizes of the joint,including the weld width of the lower plate(L),the weld depth of the lower plate(P),and the minimum distance from the weld root to the weld surface(R,the minimum radius of the fusion zone),as well as the maximum tensile capacity of the joint,were studied.Based on the gradient boosting decision tree(GBDT)algorithm,a model for predicting feature sizes and mechanical properties of the joint was established,and the effect of the welding parameters on the feature sizes and mechanical properties was revealed.Results showed that the peak current,duty cycle,and welding speed were the important factors that influenced L and P.With in-creasing peak current and duty cycle or decreasing welding speed,L and P increased.Duty cycle and pulse frequency significantly affected R.With increasing pulse frequency and duty cycle,R increased.The feature size R was the most important factor to influence the maximum tensile capacity of the welded joint.The maximum load capacity of the welded joint could reach 12.66 kN.Relative errors of the prediction model for the feature sizes and maximum tensile capacity were both less than 3%.Therefore,the GBDT model had high prediction accuracy and generalization to pre-dict the feature sizes and tensile properties of the Fe-36Ni/304L lap joint by pulsed GTAW.