How to control the heat-affected zone during laser cutting in sheet metal customization to avoid edge hardening of parts?
Release Time : 2026-02-09
In sheet metal customization, controlling the heat-affected zone (HAZ) of laser cutting is crucial for ensuring stable edge performance of parts. The HAZ forms due to the high energy input of the laser beam, causing the local temperature of the material to rise rapidly above the phase transition point, followed by rapid solidification under the cooling effect of the assist gas. During this process, the material's grain structure changes, potentially leading to increased hardness, decreased toughness, and even microcracks in the edge area, directly affecting the machining accuracy and reliability of the parts. Therefore, precise control of the HAZ is necessary through multi-dimensional process optimization and equipment control.
Matching the laser cutting parameters for sheet metal is fundamental to controlling the HAZ. The coordinated adjustment of laser power, cutting speed, and focal point directly affects the energy density and heat input absorbed by the material. Excessive power or speed leads to excessive heat input, causing the HAZ to expand and edge hardening to intensify; conversely, insufficient power or excessive speed may result in incomplete cutting or slag buildup. In practice, dynamic adjustments are necessary based on material type and thickness. For example, when cutting sheet metal, appropriately reducing power and increasing speed can reduce heat accumulation at the edges. Simultaneously, fine-tuning the focal point ensures laser energy is concentrated along the cutting path, preventing energy spillage and edge overheating.
The selection and pressure control of the auxiliary gas significantly impact the heat-affected zone (HAZ). The gas not only removes molten material but also cools and inhibits oxidation. When cutting carbon steel, oxygen, due to its combustion-supporting properties, can improve cutting efficiency but easily leads to edge oxidation and hardening. In this case, controlling the gas pressure is crucial to balance slag removal and cooling effects. When cutting stainless steel or aluminum alloys, inert gases such as nitrogen or argon prevent oxidation reactions and reduce hardness increases in the HAZ. Furthermore, the design of the gas nozzle and airflow uniformity are equally critical. Optimizing the nozzle structure ensures stable airflow coverage of the cutting area, preventing localized overheating.
Material properties and pretreatment processes are implicit factors in HAZ control. Differences in the thermal conductivity, melting point, and grain structure of sheet metal result in varying absorption and conduction characteristics of laser energy. For example, aluminum alloys require higher power densities due to their high thermal conductivity, while titanium alloys require more stringent cooling control due to their low thermal conductivity. Pre-cutting surface cleaning and smoothing treatment can reduce energy fluctuations caused by impurities or deformation. For high-hardness or heat-sensitive materials, preheating can reduce the temperature gradient during cutting and alleviate edge hardening.
Equipment precision and stability are the hardware foundation for controlling the heat-affected zone. The power stability of the laser, beam quality, and the dynamic response capability of the cutting head directly affect the uniformity of energy output. High-precision guideways and servo systems ensure smooth cutting head movement, avoiding localized overheating due to vibration or path deviation. Automatic focusing compensates for surface unevenness in real time, maintaining accurate focal position. Furthermore, regular equipment maintenance and calibration, such as cleaning optical lenses and checking gas pipeline seals, prevent energy loss or gas leakage due to equipment aging, ensuring long-term stability of the cutting process.
Cutting path planning and process strategy optimization can further reduce the impact of the heat-affected zone. For example, using pulse cutting instead of continuous cutting reduces heat accumulation through intermittent energy input; for complex-shaped parts, optimizing the cutting sequence avoids reheating the same area; and setting cooling points at sharp corners or small holes, using paused cutting and auxiliary gas purging to lower local temperatures. These process strategies effectively disperse heat and reduce the risk of edge hardening.
Post-processing is the final step in perfecting heat-affected zone control. After cutting, removing the edge oxide layer and slag through sandblasting, grinding, or chemical pickling improves surface quality; for high-hardness edges, local annealing eliminates residual stress and restores material toughness. Furthermore, online monitoring technologies, such as infrared thermography or hardness testing, can assess the heat-affected zone status in real time, providing data support for process adjustments.