Kyle, I worked at Caterpillar from 1978 to 1982. One of my duties included the creation of the dividing factors for boron grade steels for their 1E38 specification. Got into a rather heated discussion with my boss about regression analyses. I believe Caterpillar finally codified 1E38 (now in 1E24) into the ASTM A255 standard long after I left Cat. During the late 70's there were two conference proceedings on hardenability and boron. One of the European contributions bounded the B, Al and free nitrogen to a range. I have always called it the Ugine-Aciers test. See S.K. Banerji and J.E. Morral, Boron in Steel, TMS-AIME Conference Proc. Sept. 18, 1979 p.11. My workbook attempts to incorporate that test and includes the alloy factors used by Caterpillar (1E38/ASTM A255) to reduce the boron effectiveness. There is also some interesting synergy between AlN and BN. For example, if first solution treated at 1250°C, B, N, and Al can be in solution. Upon cooling BN forms preferentially, but is eventual displaced to form AlN. See S.K. Banerji and J.E. Morral, Boron in Steel, TMS-AIME Conference Proc. Sept. 18, 1979 p.46. Now you have a kinetics mess dealing with B effectiveness. One of the pitfalls of ASTM A255 is the loss of the grain size effect on hardenability. I was able to work that back into the calculation while maintaining the Caterpillar modified carbon factors.
All that said, I'm amazed that any continuously cast B steel has a boron effectiveness.
------------------------------
David Van Aken
Missouri University of Science
Rolla MO
------------------------------
Original Message:
Sent: 01-24-2021 07:43
From: Kyle Gibson
Subject: Hardenability of H steels, Boron treated steels, for Caterpillar Tractor and John Deere.
David and Paul,
While at U.S. Steel(now Mittal), and Quanex MacSteel(now Gerdau), from 1980 to 1989, I reviewed 10,000 to 20,000 heat numbers, for production of
Boron treated, Silicon-Aluminum killed steels. This was done to promote consistency within Caterpillar Tractor and John Deere heat treating lines for their equipment and parts production lines. In these studies, I took the best 10 production heats, and compared them to the absolute 10 worst heats ( hardenability wise, heat treating wise, and scrap rate wise ), to come up with best practice on generic grades, H grades, Boron grades, especially for the T-1 steels, and military grades. As you can imagine, it was highly confidential, copyright protected, and very eye-opening for efficiency and scrap rates.
I too, feel the need before I retire, to formalize the body of knowledge, set forth before us, by some of the greats like George VanderVoort (Micro-structures) and Deming(statistics). Multilevel regression analyses were part of the studies, but the bottom line was consistency, and doing it right the first time, to reduce re-heat treatments/repours, which were never as good as the initial heat treatments, and wasted so much manpower/resources, in so many ways.
Respectfully,
Kyle Gibson
Argen Labs
TBRC Chair