Abstract
There is no discussion that bainite has been under the spotlight of both academic research and industrial developments in the steel industry for the past 30 years. Bainitic forging steels have long been promised to a bright future with many examples already discussed in the mid-1980s. Thirty years later, it is interesting to see whether these materials have held up to expectations and what is their current status as hot forging steel grades. Successes and difficulties are discussed over the experience at Ascometal in designing and producing bainitic steels. Further from but getting perhaps closer to industrial applications, the topic of “nanostructured” bainite or “superbainite” has attracted considerable attention over the past 15 years. Recent efforts have focused on evaluating the performances of such materials for various applications, beyond looking at basic tensile strength. This implies understanding the tensile ductility, fatigue properties and wear resistance of such materials for example, but also comparing the results to existing steel grades and other manufacturing methods, and considering the costs of the different alternatives. An overview of some recent results is provided, and collateral benefits in the investigations of these materials are also presented.
Kurzfassung
Es steht außer Frage, dass Bainit in den vergangenen 30 Jahren in der Stahlindustrie sowohl in der akademischen Forschung als auch in der industriellen Entwicklung im Rampenlicht stand. Lange wurde bainitschen Schmiedestählen eine glänzende Zukunft vorausgesagt, was bereits Mitte der 1980er anhand vieler Beispiele diskutiert wurde. 30 Jahre später ist es interessant zu sehen, ob diese Materialien unseren Erwartungen entsprochen haben und wie der derzeitige Stand bezüglich der Warmschmiedestahl-Güteklassen ist. Erfolge und Schwierigkeiten werden anhand der Erfahrungen bei Ascometal beim Designen und bei der Herstellung von bainitischem Stahl diskutiert. Auf dem Weg zur industriellen Anwendung ist das Thema “nanostrukturierter Bainit” innerhalb der letzten 15 Jahre auf Interesse gestoßen. Dabei konzentrierten sich in den letzten Jahren die Arbeiten auf spezifische Fragestellungen, die über die Analyse der Zugfestigkeit hinausgingen. Beispielsweise erfolgte eine Bewertung der Duktilität oder des Ermüdungs- bzw. Verschleißverhaltens im Vergleich zu bestehenden Stahlgüten und unter Berücksichtigung der Herstellungskosten. Es wird ein Überblick über neuere Ergebnisse und daraus gewonnene Erkenntnisse gegeben.
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