Method for simulating generation of P92 steel welding seam metal fine cracks

Abstract

The invention discloses a method for simulating generation of P92 steel welding seam metal fine cracks. The method comprises the following steps of: (1) analyzing welding thermal input and constraint stress in a practical welding process; (2) processing a P92 steel test block, forming a U-shaped groove, and preserving a thickness of 20 millimeters at the bottom of the groove to increase the constraint stress of the test block; (3) sticking three groups of high-temperature strain foils to the bottom of the test block, and connecting with a stress tester; (4) applying tension stress to the upper parts of both sides of the test block groove before welding, making sure that the bottom of the test block reaches the pressure stress value of 100-150MPa by testing through the stress tester, welding, and fixing an external tension stress value in a welding process to apply relatively stable external tension stress to the test block; (5) after welding, annealing at a high temperature, wherein the welding in the step (4) refers to shielded metal arc welding; and (6) detecting internal cracks of welding seams by using a phase resonance, TOFD (Time Of Flight Diffraction) or ultrasonic method. In the method, factors such as the forming process, textures, mechanics and the like generating P92 steel welding seam metal fine cracks under a field practical condition are researched, so that a measure for preventing the fine cracks is found conveniently, and a welding technology and a method for practical welding conditions are provided.

Description

technical field [0001] The invention belongs to the field of metal materials, in particular to a method for simulating and generating micro-cracks in weld metal of P92 steel. Background technique [0002] At present, supercritical unit is a relatively mature advanced power generation technology in the world. Due to its unique advantages of energy saving and environmental protection, it has been widely used in thermal power generation and has become the main development trend of thermal power generation in China. At present, in the ultra-supercritical thermal power units that have been built in my country, a large number of P92 ferritic heat-resistant steels are used. Because of its high high-temperature strength and creep resistance, this steel is widely used in the headers and main steam line. [0003] Although P92 steel has been widely used in my country's ultra-supercritical units, and has accumulated some experience in design, manufacturing, welding, installation, and op...

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Problems solved by technology

[0003] Although P92 steel has been widely used in my country's ultra-supercritical units, and has accumulated some experience in design, manufacturing, welding, installation, and operation supervision, but in the process of making and installing the main steam pipeline, the P92 steel A large number of micro-cracks are generally produced inside the weld metal. Different from the traditional weld metal hot cracks and delayed cracks, this type of crack is a low-temperature brittle crack produced during the cooling process of the weld metal. The crack length is short and the aspect ratio is small. , posing a threat to the safe and stable operation of the unit

However, in the P92 steel welding process evaluation conducted by domestic manufacturers and power construction and installation units, no such cracks are easily formed in the weld metal, making it difficult for the qualified welding process to adapt to the actual production conditions and installation conditions. Problems to be Solved Urgently in the Construction and Restoration Technology of Ultra-supercritical Units

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