Prediction of microstructure composition in steel plate heated using high power Yb:YAG laser radiation

Marcin Kubiak,I Malujda,Ł Warguła,D Wojtkowiak,M Dudziak,K Talaśka,J Górecki,D Wilczyński,M Berdychowski,P Krawiec

doi:10.1051/matecconf/201925402023

Abstract

This work concerns numerical modelling and computer simulations of temperature field and phase transformations during Yb:YAG laser heating of sheets made of S355 steel. The distribution of laser power emitted by Trumpf laser head D70 is used in the analysis. The heat source is modelled on the basis of interpolation algorithms using geostatistical kriging method. Coupled heat transfer and fluid flow in the fusion zone are described respectively by transient heat transfer equation with convective term and Navier-Stokes equation. The kinetics of phase transformations and volumetric fractions of arising phases are obtained on the basis of Johnson-Mehl-Avrami (JMA) and Koistinen-Marburger (KM) models. Continuous Heating Transformation (CHT) diagram is used for heating process and Continuous Cooling Transformation (CCT) diagram is used for heated steel with the decomposition of final volume fractions of phases transformed form austenite dependant on cooling rates.

Highlights

Laser beam processing of steel has increasing application in many industries, mainly due to high process speed and good quality of the product as well as a small zone of thermal influence on the material
As a result phase transformations in solid state are present, which leads to the formation of various structures in heat affected zone (HAZ) with differing mechanical properties [1, 2]
Simulations of the Yb:YAG laser heating process are performed for S355 steel sheets with dimensions 250 mm in length, 50 mm in width, with a thickness of 5 mm, assuming laser head movement speed v = 3 m/min, the focusing point on the top surface of heated element (z = 0) and laser power: Q = 900 W

Summary

Introduction

Laser beam processing of steel has increasing application in many industries, mainly due to high process speed and good quality of the product as well as a small zone of thermal influence on the material. The concentration of a laser heat energy leads to the generation of high cooling rates in heat affected zone (HAZ). As a result phase transformations in solid state are present, which leads to the formation of various structures in HAZ with differing mechanical properties [1, 2]. The material in this process is heated to various temperatures. High heating rates and various maximum heating temperatures of steel occur in the case of laser heating [7,8,9,10] affect the kinetics of phase transformation in the solid state.

Thermal phenomena

Phase transformation in solid state

Results

Conclusions