Heat-affected zone

About: Heat-affected zone is a research topic. Over the lifetime, 18787 publications have been published within this topic receiving 231744 citations.

Investigation of the effects of basic laser material interaction parameters in laser welding

Abstract: The depth of penetration achieved in continuous wave (CW) laser welding results from a balance of many complicated phenomena, which are linked with the characteristics of the heat source. In this work, the laser welding process has been investigated in terms of basic laser material interaction parameters: power density and interaction time. It has been shown that these two parameters are insufficient to characterize the laser welding process. Thus, a third parameter, specific point energy, has been introduced, which along with the power density and the interaction time allowed the welding process to be uniquely defined. It has been shown that the depth of penetration is mainly controlled by the power density and the specific point energy, whilst the weld width is controlled by the interaction time.

Explanation of penetration depth variation during laser welding under variable ambient pressure

Abstract: It has been observed that the penetration depth during laser welding (LW) under vacuum or reduced ambient pressure could be significantly greater than that during welding under atmospheric pressure. Previous explanations of this phenomenon usually limit to specific wavelength laser welding and have difficulties in explaining why the variation will disappear, as the welding speed increases. Here, we propose that this variation is caused by the temperature difference of keyhole wall under variable ambient pressure based on a correct physical description of related processes. A new surface pressure model, dependent on ambient pressure, is proposed for describing the evaporation process during laser material interaction under variable ambient pressure. For laser welding of a 304 stainless steel with 2.0 kW laser power and 3 m/min welding speed, it is shown that the average keyhole wall temperature is around 2900 K under atmospheric pressure, and only around 2300 K under vacuum, which results in significant penetration depth variations. Interestingly, it is also shown that as the welding speed increases, the average temperature of the front keyhole wall gradually rises due to the reduction of the mean incident angle of laser, and the magnitude of this increase is larger in welding under vacuum than under atmospheric pressure. It allows us to explain why the penetration depth improvement decreases to zero with the increase of welding speed.

Characterization and prediction of the heat-affected zone in a laser-assisted mechanical micromachining process

Abstract: Laser-assisted mechanical micromachining (LAMM) is a micro-cutting method that employs highly localized thermal softening of the material by continuous wave laser irradiation focused in front of a miniature cutting tool However, since it is a heat-assisted process, it can induce a detrimental heat-affected zone (HAZ) in the part This paper focuses on characterization and prediction of the HAZ produced in a LAMM-based micro-grooving process The heat-affected zone generated by laser heating of H-13 mold steel (42 HRC) at different laser scanning speeds is analyzed for changes in microstructure and microhardness A 3-D transient finite element model for a moving Gaussian laser heat source is developed to predict the temperature distribution in the workpiece material The model prediction error is found to be in the 5–15% range with most values falling within 10% of the measured temperatures The predicted temperature distribution is correlated with the HAZ and a critical temperature range (840–890 °C) corresponding to the maximum depth of the HAZ is identified using a combination of metallography, hardness testing, and thermal modeling