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电站高温紧固螺栓在长期运行中,易产生热脆、蠕变、疲劳、应力腐蚀和裂纹等缺陷。根据DL/T439-2006《火力发电厂高温紧固件技术导则》,对其进行检测是十分必要的,检测项目主要包括光谱、硬度、金相和无损检测等。由于电站高温紧固螺栓的长径比(L/D)大,规格杂数量多,在役检测受到工期限制,因此其无损检测以超声检测为主,辅以其他检测方法。检测标准为DL/T694-1999《高温紧固螺栓超声波检测技术导则》和JB/T4730-2005《承压设备无损检测》。其中,JB/T4730-2005的“标准释义”中明确表述:“对于制造和在用螺栓件(坯件),由于螺纹已经加工,螺纹根部裂纹可采用小直径纵波和小角度纵波斜探头来检测,其检测灵敏度可采用根部裂纹或平底孔作为参考反射体来校正。”
Power station high temperature fastening bolts in the long run, easy to produce hot brittle, creep, fatigue, stress corrosion and cracks and other defects. According to DL / T439-2006 “Technical Guidelines for High Temperature Fasteners in Thermal Power Plants”, it is very necessary to test them. The testing items mainly include spectrum, hardness, metallography and non-destructive testing. Due to the large aspect ratio (L / D) of the high temperature fastening bolts of the power plant and the large number of specifications, the in-service inspection is subject to the construction period limitation. Therefore, the non-destructive testing is mainly based on ultrasonic testing, which is supported by other testing methods. Testing standards for the DL / T694-1999 “high temperature fastening bolts Ultrasonic Testing Technology Guidelines” and JB / T4730-2005 “pressure equipment nondestructive testing.” Which, JB / T4730-2005 “standard interpretation ” made it clear: "For manufacturing and in the use of bolts (blanks), because the thread has been processed, the root of the crack can be used to crack small diameter longitudinal waves and small oblique wave Probe to detect, the detection sensitivity can be used as a root crack or flat bottom hole as a reference reflector to correct.