A discussion of laser heat treating begun in Heat Treat Today’s Air & Atmosphere 2024 print edition would not be complete without highlighting key sustainability advantages of this new technology. In this Technical Tuesday installment, guest columnist Aravind Jonnalagada (AJ), CTO and co-founder of Synergy Additive Manufacturing LLC, explores how sustainability and energy-efficiency are driven by precision heat application and minimal to zero distortion. The first part, “Advantages of Laser Heat Treatment: Precision, Consistency, and Cost Savings”, appeared on April 2, 2024, in Heat Treat Today, as well as in Heat Treat Today’s January/February 2024 Air & Atmosphere print edition.
This informative piece was first released in Heat Treat Today’s May 2024 Sustainability Heat Treat print edition.
Laser heat treating is a transformative process that promises superior performance and sustainable practices. Laser heat treating epitomizes precision in surface heat treatment techniques, targeting localized heating of steel or cast-iron components. Laser radiation raises the surface temperature of the metal in the range of 1652°F to 2552°F (900°C to 1400°C), inducing a transformation from ferritic to austenitic structure on the metal surface. As the laser beam traverses the material, the bulk of the component self-quenches the heated zone. During this process, carbon particles are deposited in the high temperature lattice structure and cannot diffuse outward because of quick cool down resulting in the formation of hard martensite to a case depth up to 0.080” (2 mm), crucial for enhancing material properties.
Sustainability through Energy Efficiency
When considering the energy consumption of a typical laser heat treating operation, it’s essential to acknowledge the continuous advancements in laser technology. Modern laser heat treating systems integrate high-power lasers, water chillers, and motion systems, such as robots or CNC machines. With a typical wall plug efficiency of around 50% for diode lasers, these systems represent a significant improvement in energy utilization compared to conventional methods. The typical energy consumption cost for running a 6 kW laser heat treating system is $20-$30/day. The calculation is based on an 8-hour shift with a duty cycle of 80% calculated at national average electric cost of 15.45 cents/kilowatt-hour.
Self-Quenching Mechanism
Laser heat treating operates on the essential principle of self-quenching, leveraging the bulk mass of the material for rapid cooling. This eliminates the dependence on quenchants required in flame and induction heat treating processes, further reducing environmental impact and operational costs.
Precision and Minimal Distortion
At the heart of laser heat treating lies its sustainable and energy-efficient attributes, driven by two fundamental features: precision heat application and minimal to zero distortion of components post-heat treatment. When compared to the conventional methods such as flame and induction hardening, laser heat treatment offers significantly localized heating. This precision allows for targeted heat treatment within millimeter precision right where the hardness is needed, optimizing energy utilization and operational efficiency. Furthermore, the high-power density of lasers enables hardening with minimal to zero distortion, eliminating or reducing the need for subsequent machining operations like hard milling or grinding.
Source: Autodie LLC
A Case Study of Laser Heat Treating in Automotive Stamping Dies
The image above identifies process steps typically involved in construction of automotive stamping dies. During the process of manufacturing automotive stamping dies, the cast dies are first soft milled, intentionally leaving between 0.015” and 0.020” of extra stock material on the milled surfaces. This is done to account for any distortions that will result from the subsequent conventional heat treatment processes such as flame or induction. After heat treating, the dies are then hard milled back to tolerance and assembled.
In the laser heat treating process, by contrast, dies are finish machined to final tolerance in the first step and then laser heat treated without distortion. No secondary hard milling operation is necessary. Typical cost savings for our automotive tool and die customer exceeds over 20% due to elimination of hard milling operation. Total energy reduction is significant, although not computed here. This may result in savings if carbon credits become monetized.
Laser heat treating’s precision, efficiency, and minimal environmental footprint position it as an environmentally friendly option for heat treat operations. As industries continue to prioritize sustainability, laser heat treating may set new standards for excellence and environmental stewardship.
About the Author:
CTO and Co-Founder
Synergy Additive Manufacturing LLC
Source: LinkedIn
Aravind Jonnalagadda (AJ) is the CTO and co-founder of Synergy Additive Manufacturing LLC. With over 15 years of experience, AJ and Synergy Additive Manufacturing LLC provide high-level laser systems and laser heat treating, specializing in high power laser-based solutions for complex manufacturing challenges related to wear, corrosion, and tool life. Synergy provides laser systems and job shop services for laser heat treating, metal based additive manufacturing, and laser welding.
For more information: Contact AJ at aravind@synergyadditive.com or synergyadditive.com/laser-heat-treating.
