Advantages of Laser Heat Treatment, Part 2: Energy Efficiency, Sustainability, and Precision

June 25, 2024 / AUTOMOTIVE HEAT TREAT TECHNICAL CONTENT, FEATURED NEWS, HARDENING TECHNICAL CONTENT, OP-ED

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.

Case Study image; 16 small boxes of auto parts undergoing die machining, laser heat treat; blue inset box — Comparison of the die construction process before and after laser hardening
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:

Aravind Jonnalagadda
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.

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Advantages of Laser Heat Treatment: Precision, Consistency, and Cost Savings

Laser heat treating, a form of case hardening, offers substantial advantages when distortion is a critical concern in manufacturing operations. Traditional heat treating processes often lead to metal distortion, necessitating additional post-finishing operations like hard milling or grinding to meet dimensional tolerances.

This Technical Tuesday article was originally published in first published in Heat Treat Today’s January/February 2024 Air & Atmosphere print edition.

In laser heat treating, a laser (typically with a spot size ranging from 0.5″ x 0.5″ to 2″ x 2″) is employed to illuminate the metal part’s surface. This results in a precise and rapid delivery of high-energy heat, elevating the metal’s surface to the desired transition temperature swiftly. The metal’s thermal mass facilitates rapid quenching of the heated region resulting in high hardness.

Key Benefits of Laser Heat Treating

Consistent Hardness Depth

Laser heat treatment achieves consistent hardness and hardness depth by precisely delivering high energy to the metal. Multiparameter, millisecond-speed feedback control of temperature ensures exacting specifications are met.

Minimal to Zero Distortion

Due to high-energy density, laser heat treatment inherently minimizes distortion. This feature is particularly advantageous for a variety of components ranging from large automotive dies to gears, bearings, and shafts resulting in minimal to zero distortion.

Precise Application of Beam Energy

Unlike conventional processes, the laser spot delivers heat precisely to the intended area, minimizing or eliminating heating of adjoining areas. This is specifically beneficial in surface wear applications, allowing the material to be hardened on the surface while leaving the rest in a medium-hard or soft state, giving the component both hardness and ductility.

Figure 1. Laser heat treating of automotive stamping die constructed from D6510 cast iron material (Source: Synergy Additive Manufacturing LLC)

No Hard Milling or Grinding Required

The low-to-zero-dimensional distortion of laser heat treatment reduces or eliminates the need for hard milling or grinding operations. Post heat treatment material removal is limited to small amounts removable by polishing. Eliminating hard milling or grinding operations saves substantial costs in the overall manufacturing process of the component. Our typical tool and die customers have seen over 20% cost savings by switching over to laser heat treating.

Figure 2. Laser heat treating of machine tool
components (Source: Synergy Additive Manufacturing LLC)

Applicable for a Large Variety of Materials

Any metal with 0.2% or more carbon content is laser heat treatable. Hardness on laser heat treated materials typically reaches the theoretical maximum limit of the material. Many commonly used steels and cast irons in automotive industry such as A2, S7, D2, H13, 4140, P20, D6510, G2500, etc. are routinely laser heat treated. A more exhaustive list of materials is available at synergyadditive.com/laser-heat-treating.

Conclusions

Laser heat treatment is poised to witness increased adoption in the automotive and other metal part manufacturing sectors. The adoption of this process faces no significant barriers, aside from the typical challenges encountered by emerging technologies, such as lack of familiarity, limited hard data, and a shortage of existing suppliers. The substantial savings, measured in terms of cost, schedule, quality, and energy reduction, provide robust support for the continued embrace of laser heat treatment in manufacturing processes.