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Induction heat treatment of steel bars

Joachim Plust of EFD Induction Germany discusses how integrated induction heating leads to better, faster and cheaper heat treatment of steel bars.

Induction heat treatment of steel bars 



Treating steel bars in order to enhance torsion characteristics, reduce alloy components, etc. has long been a well-known process. One traditional treatment process involves using continuous furnaces. However, the use of continuous furnaces makes it extremely difficult to control and monitor the heat treatment process.



But there is a better way: inline heat treatment. This alternative, which hardens and tempers at high temperatures without interruption, is reliably achieved by processing the bars individually with integrated induction heating. Over the years EFD Induction has worked closely with numerous customers in the steel industry bar industry. The results of this cooperation are sophisticated induction installations that deliver stable, flexible and amazingly reproducible heating processes to customers worldwide. Inline heat treatment with EFD Induction equipment typically processes steel bars with a diameter of 20–140 mm. The length of the bars ranges from 5–18 meters. The hardening temperature is approximately 900°C and the tempering temperature is in the region of 700°C.



Although conditions vary from customer to customer, a number of key benefits are common to users of inline induction heat treatment:

  • Enhancement of material properties, such as toughness, reduction of area, etc.
  • Optimized consumption values
  • No starting phases
  • Quick batch changes – small batches
  • Improved results in terms of homogeneity
  • Clean processes; oils and fumes are extracted and cleaned


Examples of installations for bar steel:

  • For an output of 1 ton per hour the induction power used is 250 kW, 10 kHz for hardening and 200 kW, 6 kHz for tempering. The layout of this installation, including inlet- and outlet magazine and cooling units, is approx. 26 x 7 meters.
  • For an output of 3.5 tons per hour the induction power used is 600 kW + 250 kW, 10 kHz for hardening and 600 kW + 100 kW, 6 kHz for tempering. The layout of this installation, including inlet- and outlet magazine and cooling units, is approx. 44 x 10 meters.

Higher outputs are possible.