火力发电厂大型铸钢件的焊接修复及安全评估

Welding Repair and Safety Assessment of Cast Steel Parts in Fossil Fuel Power Plants

分别以汽轮机汽缸和主给水管道电动阀的焊接修复及安全性评估为例,对铸钢件的常用焊接修复方法进行了分析和探讨。火力发电厂大型铸钢件壁厚大且厚度分布不均匀,在现场焊接修复后难以实施局部焊后热处理,因此通常采用异质冷焊修复方法进行修复。通过汽轮机汽缸的焊接修复表明在严格控制焊接工艺下,异质冷焊修复工艺应用于火力发电厂铸钢件的现场修复是切实可行的。针对电厂实际运行工况下(包括启停等过程)运行后有时镍基焊缝会发生开裂的情况,应严格控制焊接修复工艺并采取适当的消除焊接残余应力的措施。

The welding repair and safety assessment methods of cast steel parts such as steam turbine cylinder and motorized valve for main feed water pipe in fossil fuel power plants were introduced and analyzed.With heavy thickness and wall unevenness of cast steel parts,the implementation of post-weld heat treatment（PWHT） on-site after welding repair was very difficult.Usually arc-cold welding was adopted for cast steel parts welding repair.Nickel-base welding consumables were adopted for cast steel parts repairing.It shows that the welding repair of steam turbine cylinder by cold-welding method were practical and successful.In order to prevent the nickel-base repaired weldments from cracking on operating conditions（including start-up and shutdown）,the welding repair process should be carried out strictly.And proper welding residual stress relieving should be adopted to improving its fatigue and crack resistance.