Subcritical vs. Intercritical Annealing for cold heading
Subcritical vs. Intercritical Annealing for cold heading
(OP)
I am working on reducing cycle time and temperatures for a variety of low and medium carbon steel coils for subsequent cold heading (bolt manufacturing).
I always had the belief that inter-critical annealing is better because although it uses higher temperatures it allows for shorter cycle times (controlling process bottlenecking) but the attached paper seems to propose the opposite. (It's only the abstract/first page).
What annealing philosophies are used to produce a more cost effective/less time extensive spherodized structure? Thanks in advance for your help!!

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I always had the belief that inter-critical annealing is better because although it uses higher temperatures it allows for shorter cycle times (controlling process bottlenecking) but the attached paper seems to propose the opposite. (It's only the abstract/first page).
What annealing philosophies are used to produce a more cost effective/less time extensive spherodized structure? Thanks in advance for your help!!
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RE: Subcritical vs. Intercritical Annealing for cold heading
Regards,
Cory
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RE: Subcritical vs. Intercritical Annealing for cold heading
In general, however, I think that for plain carbon steels, the inter-critical route would lead to shorter times. With low-alloy steels, however, sub-critical can be faster because long times are needed once you have dropped back below the A1. The alloying elements slow the austenite transformation so long hold times are needed to prevent lower temperature transformation products from forming.
rp
RE: Subcritical vs. Intercritical Annealing for cold heading
If you are talking about annealing cold-drawn wire, then there is essentially no contest: the strain induced during the cold-drawing process accelerates the breakdown of pearlite during subcritical annealing. The research by O'Brien & Hosford (also published in Industrial Heating and Met Trans) was very good. Some other good references on this subject are as follows:
Robert L. Draker and Krish Naidu, "Control of Surface Carbon During Intercritical And Subcritical Annealing", Wire Journal International, January 2000, p 96-103.
Krish Naidu, et al, "Quality annealing economically", Wire Journal International, May 1983, p 63-73.
D. Hernández-Silva, et al, "The Spheroidization of Cementite in a Medium Carbon Steel by Means of Subcritical and Intercritical Annealing", ISIJ International vol 32, no. 12 (1992)
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K. Aihara & S. Kanbara, "Influence of Prior Structure upon Spheroidization Rate and Cold Forgeability of Annealed Wire", The Sumitomo Search, No. 42, April 1990, p 1-8.
R. Kienreich, et al, "Improved Cold Formability by Thermo-Mechanical Rod Rolling", Steel Research International, Vol 74 (No. 5), 2003, p 304–310.
H. Hata, et al, "Development of High Quality Wire Rod through Thermomechanical Control Processes", Kobelco Technology Review, No. 25, April 2002, p 25–29.
T. Ochi, et al, "Special Steel Bars and Wire Rods Contribute to Eliminate Manufacturing Processes for Mechanical Parts", Nippon Steel Technical Report, No. 80, July 1999, p 9–15.
Ebner Industrieofenbau GmbH
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RE: Subcritical vs. Intercritical Annealing for cold heading
RE: Subcritical vs. Intercritical Annealing for cold heading