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SPRON®, a high-performance metal material created from watch springs

What is SPRON?

SPRON is the brand name of a high-performance metal material from Seiko Instruments Inc. The word was created by combining SPRING and MICRON. As the name suggests, SPRON boasts excellent properties as a precision spring material and in its finished size resulting from precision processing with micron accuracy.
SPRON was created as a spring material, to serve as a power source in mechanical watches.
Taking advantage of its features including high elasticity, strength, corrosion resistance, and heat resistance, this material has been used for springs as power sources in watches for more than 50 years.
Watches are not the only applications of SPRON. Taking advantage of its metallic properties, this material is also used in demanding environments where durability and corrosion resistance are required, such as for valves enduring corrosive gas, which are used for semiconductor devices, and for equipment for dental treatment.

History of SPRON

Until the 19th century, springs made of iron were used for mechanical watches. However, those springs had their own disadvantages: they tended to rust and become cut easily.
Watch springs need to be strong and rust-proof and retain their elasticity because they undergo repeated winding and unwinding over long periods. In addition, resistance to temperature changes and magnetization is also required for ensuring precision.
In the early 1900s, Charles Edouard Guillaume, a Swiss physicist, invented an alloy whose volume and spring force do not change significantly in response to temperature changes. This resulted in a marked reduction of temperature errors in mechanical watches.
At Seiko, we began to study excellent materials in the 1950s by collaborating with the Institute for Materials Research, Tohoku University. In 1956, we succeeded in developing SPRON, featuring minimum elasticity changes caused by temperature changes. This was enabled by using metallic cobalt instead of nickel.
Taking advantage of this excellent feature, we expanded the applications of SPRON in the 1970s, using them for devices other than watches.
At present, Seiko Instruments Inc. markets two metal materials – SPRON100 and SPRON510 with even higher performance – for a diverse array of fields.
We have also continued to improve SPRON for application in the main springs and balance springs of watches. At present, the latest SPRON530 (for main springs) and SPRON610 (for balance springs) are used for high-frequency models of Grand Seiko.

The five advantages of SPRON

  1. 1. Rust-proof (high corrosion resistance)
  2. 2. Strong (high strength and durability)
  3. 3. Doesn't get loose (super-high elasticity)
  4. 4. Doesn't get magnetized (non-magnetism)
  5. 5. Resistant to low/ high temperature
【Features of SPRON】
SPRON boasts properties that are far superior compared with those of stainless steel and nickel.

Example applications of SPRON


SPRON is highly valued for its high elasticity and durability.

  • Dental equipment (springs for handpieces)
  • Orthodontic braces


Taking advantage of its high corrosion resistance, durability, and heat resistance, SPRON is used in the demanding environments inside automobiles.

  • Automotive parts
  • Spring parts