Test method and application method for nucleation growth rule of acicular ferrite in welding process

Abstract

The invention relates to a test method and an application method of the nucleation growth rule of acicular ferrite in a welding process. The test method comprises the following steps: (1) processing EH420 ship plate steel into a sample, polishing, and putting into a crucible; (2) heating to 1350 + / -10 DEG C at a heating speed of 5 + / -0.1 DEG C / s, and keeping the temperature; (3) cooling to 800 + / -10 DEG C for the first time, and cooling to 500 + / -10 DEG C for the second time; (4) observing and recording a process of converting austenite into acicular ferrite through a high-temperature laser confocal microscope; and (5) making a length-time-temperature relation curve graph of the acicular ferrite according to the growth data of the acicular ferrite lath in the recording result, and determining the nucleation time and the temperature range of the EH420 ship plate steel for forming acicular ferrite with different sizes. The application method comprises the steps that the conversion temperature and time are estimated through a formula, the welding voltage, the welding current and the welding speed of the welding machine are adjusted, temperature and time parameters are obtained, and welding is completed. The problems of unstable weld joint performance, welding randomness and the like in the thick plate welding process can be solved.

Description

technical field [0001] The invention belongs to the technical field of metallurgical materials, and in particular relates to a method for testing and applying the law of nucleation and growth of acicular ferrite during welding. Background technique [0002] The development trend of a new generation of ship plate steel such as steel for offshore platforms and ship decks, such as large-scale, high-strength, and high-weldability requires steel plates to have higher comprehensive properties, including higher mechanical properties, while increasing their thickness. , efficient processing performance and excellent welding performance. Traditional low-alloy high-strength steel has poor weld performance (strength, toughness) after welding, poor welding efficiency, and high cost. Welding seams are prone to welding cold cracks, which brings difficulties to the welding of thick plates, extra thick plates, and large structural steels and their subsequent applications. At present, medi...

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Problems solved by technology

[0004] The structure of the heat-affected zone after traditional welding is massive ferrite and pearlite, and repeated welding experiments will cause large fluctuations in welding performance. The welding performance is poor, and the evolution of the material structure and properties during the welding process is not consistent. Clear, the transformation of the structure and properties in the actual welding process is random, and it is impossible to accurately control the deformation process of the structure in the weld area

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