q235b通信钢管塔断裂失效-河北农业大学.doc

Q235B通信钢管塔断裂失效 分析与解决方法 范文静 孙维连﹡ 王会强 孙铂 （河北农业大学机电工程学院, 保定, 071001） 摘要：Q235B碳素结构钢制造通信塔在矫直过程中出现焊接处断裂。采用扫描电镜、光学显微镜、以及力学性能测试等方法，对断裂构件进行了分析，并对化学成分和力学性能进行检测。结果表明，材料原始组织铁素体和珠光体呈带状分布，导致材料出现各向异性。在矫直过程中，应力在焊接处造成集中，超过了材料的抗弯极限，导致其发生脆性开裂。经试验，构件焊接后，采用退火工艺可消除此类故障。 关键词：Q235B；通信钢管塔；脆性开裂；失效分析 Failure Analysis and resolved Methods of Q235B Communication Tower of steel tube Fan WenJing,Sun WeiLian,Wang HuiQiang,Sun Bo Electrical and Mechanical Engineering College Agricultural University of Hebei, P.R.China, 071001 Abstract: Q235B constructional carbon steel Communication?Tower of steel tube is cracked in weld during straightening.Using of Scanning Electron Microscopy (SEM)，Metallographical examination, and Mechanical properties measurement, the cracking was analyzed. Besides,the chemical composition and mechanical properties were testing.The results show that in the primordial structure there are banded ferrite and pearlite , which brought about anisotropy . In the straighten process, The banded structure caused the stress concentration in weld. The resultant stress exceeded the ultimate bending strength of the material,and then caused the brittle cracking.When the component has been jointed, Via the examination,introduce the anneal technics could avoid this failure. Keywords:Q235B;Communication?Tower of steel tube;Brittle cracking;failure analysis 通信塔由数根圆筒形构件连结而成，圆筒周身布有翅片，与杆身焊接一体，以供通信天线安装。外形如图1所示。塔材料为Q235B焊接钢管。翅片和法兰焊在钢管上，部分钢管由于焊接应力产生弯曲，需通过矫直才能使用。具体方法是：并排两根钢管，其两端用钢丝绳固定，中心处用千斤顶外推，出现钢管在翅片与钢管焊接处发生断裂事故，为了查明断裂失效的原因，运用失效分析基本方法［1］，借助金相显微镜和扫描电镜对断口显微组织和断口形貌进行分析。 理化检验与分析 1.1化学成分检验 为了了解零件的化学成分，采用化学分析法对失效钢管材质进行分析，结果见表1。从材料成分看，该材料成分符合GB/T 1299-2000中对Q235B碳素结构钢的要求。 表1 Q235B碳素结构钢化学成分（wt﹪） Table 1 Elemental composition of Q235B constructional carbon steel (wt﹪) 项目 C Si Mn S P 样品实测值 0.17 0.23 0.46 0.014 0.020 GB/T 1299-2000 0.12～0.20 ≤0.30 0.30～0.70 ≤0.045 ≤0.045 1.2焊缝区检验 对缺陷钢管焊缝处检验，参照直缝电焊钢