Method for predicting grain size of micro-alloy steel welding coarse grained region

Abstract

The invention relates to a method for predicting the grain size of a micro-alloy steel welding coarse grained region and belongs to the field of physical measurement. The method comprises the steps that firstly, through heat simulation, information of the original austenite grain size of the micro-alloy steel welding coarse grained region under three or more different kinds of heat input is obtained; secondly, the grain growth dynamics formula which is shown in the description is set, wherein M0 and PZ are unknown constants, other parameters are known parameters, corresponding reasonable values are obtained by looking up literature, then the values of the original austenite grain size of the coarse grained region under three different kinds of heat input and the grain growth dynamics formula are fitted (through numerical integration and a finite difference method), and the values of M0 and PZ are obtained through an optimal fitting result; finally, through the grain growth dynamics formula and the fitted values of M0 and PZ, the grain size of the micro-alloy steel welding coarse grained region under different kinds of welding heat input is calculated, and the grain size of the micro-alloy steel welding coarse grained region is predicted. According to the method, the fitting and calculation process is simplified, and importance basis is provided for controlling the grain size ofthe micro-alloy steel welding coarse grained region.

Description

Technical field: [0001] The invention belongs to the field of physical measurement, and in particular relates to a method for predicting the grain size of the microalloy steel welded coarse grain zone. Background technique [0002] The welded coarse-grained zone is usually one of the weakest regions of the welded joint, and its mechanical properties represent the mechanical properties of the welded joint to a large extent. Therefore, evaluating the mechanical properties of the welded coarse-grained zone can be used to evaluate the The mechanical performance characteristics of welded joints provide an important reference. The microstructure of iron and steel materials is usually one of the most important factors determining their mechanical properties, and the grain size, as an important characterization parameter, has always been considered to be one of the most important indicators for evaluating whether the mechanical properties of the welded coarse-grained zone have deter...

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Problems solved by technology

The main reason is that in the thermal cycle of the welding coarse-grained zone, when the grain grows, it will be pinned by the second phase particles in the microalloyed steel, and the welding thermal cycle itself will also affect the thermal stability of the second phase , as the thermal cycle time and temperature change, the pinning effect of the second phase particles will also change, and the welding thermal cycle is a typical non-thermodynamic equilibrium thermal process. Therefore, the rationality of the results obtained by using the grain growth kinetic formula to calculate the grain size of the microalloy steel welding coarse grain zone depends on whether the micro Precise description of thermal stability of second phase particles in alloy steel

Although the basic formulation of the grain growth kinetics formula is publicly available, different researchers have different approaches on how to approximate the pinning effect of the second relative grain growth in microalloyed steels during the welding heat process , so the reliability of the calculated results will be different

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