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Laser Hardening

Laser Hardening Technology for Metallic Materials

Technology

Heat treatment is a process in which metallic materials are heated to
a certain temperature in a particular manner to alter their internal
structure to obtain the desired mechanical properties. Laser
hardening leading to changes on the surface of materials is very
similar to the conventional high-frequency heat treatment
(Induction Hardening) method. However, laser hardening has
advantages including the absence of dimensional changes to the
parent materials after the treatment, high surface hardness by
configuring the dense tissue, and the elimination of the need for a
separate cooling step. In addition, selective hardening can be applied
on necessary parts, such as complex mechanical parts, in the three-
dimensional shape, mold products, and Thompson blade. By
measuring and controlling the surface temperature of the parent
metal in real time with a pyrometer, it is possible to obtain stable
product quality in large-volume and low-volume production
processes.

The surface hardness after laser hardening depends on the carbon
content of the parent metal, typically > 53 - 65Hrc. The effective
hardening depth is between 0.8 mm and 1.5 mm, and the width can
be from single-digit mm to several dozens of millimeters in
accordance with the laser output.

Until the early 2000s, CO2 laser had been universally used for the
laser hardening process. Since then, high-power lasers, which have a
high absorption rate in metal materials, have been developed,
Currently, a wide variety of high-power lasers such as semiconductor
lasers, disc lasers, and fiber lasers are being used.

As an alternative method of induction hardening, laser hardening
technology is being actively applied to the press mold, injection
mold, and automobile parts in the automotive industry. Its
application area is being expanded to various areas ranging from
shipbuilding, steel, and machinery to the electronics industry that
demand increased hardness and strength of a product through
local heat treatment.

The basic principle of laser hardening is heating up the parent
material up to the point just below the melting temperature by
applying a laser beam with a high energy density on the surface of
metallic materials, and bringing about a change in the material by a
fast cool down. The laser beam applied on the surface of the parent
material will be converted into heat energy to heat up the surface,
and the subsequent temperature drop through conductivity of the
material (Self-Quenching) increases the hardness and strength of the
material.

[ Laser Hardening Principle ]

Laser Hardening Principle

Pros

  • Possible to apply heat hardening to only the necessary part
  • Improves the heat-hardening quality by monitoring and controlling the temperature in real time
  • Improves work flexibility and productivity by using various types of lasers suitable for the target materials
  • Achieves highly stable and uniform annealing effects and minimization of deformation with self-quenching effect
  • Achieves very reliable effects even on small products regardless of output, size, and weight of the product

Applications of Laser Hardening

  • Can be applied to almost all tool steel, cast iron, carbon steel, and chromium steel alloys, etc.
  • Carbon contents requirements: > 0.2% C
  • Applied products: automotive, electronics, shipbuilding, aviation
    parts, injection and press molds, cutting tools, large turbines, gear
    threads, blades, various tools, etc.

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