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Recent Developments in Sheet Steels

from a Forging Perspective and Outlook

C J Van Tyne

Advanced Steel Processing and Products Research Center

Colorado School of Mines

Golden, CO USA

Forging Technical Conference

September 12, 2018

Long Beach, CA

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ASPPRC

Concentrating on research at the

interface between producers and users of steel.

CSMCSMCSM

Advanced Steel

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Products Research

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ASPPRC Sponsors

AK Steel

Algoma

AMG Vanadiu

ArcelorMittal

Baoshan Iron and Steel

Bekaert

Blount International

Caterpillar Incorporated

CBMM North America

Chevron Energy

Climax Molybdenum

Deere and Company

Essar Steel Algoma

Evraz Inc. NA

FCA US LLC

General Motors Corporation

Gerdau

Gestamp

Kobe Steel

Los Alamos National Laboratory

Nexteer Automotive

Nucor Steel

POSCO

Precision Castparts Corp

Saudi Basic Industries

SSAB Americas

Tata Steel Europe

Ternium Mexico

Timken Steel

Thyssenkrupp Steel

United States Steel Division, of USX

voestalpine Stahl GmbH

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• Major developments in sheet steels over last

decade.

• Possible opportunities for forging companies

• Objectives:

1) Justify why forgers should be aware of sheet

steel metallurgy.

2) Describe some of the recent developments.

3) Speculate about possible opportunities in the

coming years.

Background and Objectives

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• Microalloyed forging steels

• Major opportunity of forging companies

• Low total cost manufacturing

• Good for certain markets

• Where were microalloyed steels first developed

and used in a major way?

A Bit of History

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• A major large scale use was in steel plate in

early 1970s although patents in 1939-41.

• Produced by Japan for use in the 800 mile

Alaskan pipeline.

• Pipe made by the UOE process using a large

hydraulic press.

Microalloyed Steels

Gray MJ and Siciliano F. High Strength Microalloyed Linepipe. Microalloyed Steel Institute; 2009.

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• Steel metallurgy continues to evolve to meet the

needs of society.

• There is significant time from initial idea/patent

to large scale use.

• Forging steels may develop from research done

on other steel products.

Implications

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• Automotive industry uses large quantities of

steel.

• Vehicles need to become lighter and stronger.

• Lighter to increase fuel economy and to reduce

emissions.

• Stronger to improve passenger safety.

• Steel Companies are developing sheet steels

with high strength and higher toughness.

• Higher strength means less steel and lighter vehicle

• Higher strength often means less toughness

Drivers of Recent Developments in Sheet

Steels

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• First Generation

Automotive Sheet Steels

www.tf.uni-kiel.de/matwis/amat/iss/kap_9/advanced/t9_2_1b.html

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• Second Generation

Automotive Sheet Steels

Suwanpinij P, The Synchrotron Radiation for Steel Research, Adv in Mat Sci and Engr, 2016.

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• Third Generation (Gen3) Steels

Automotive Sheet Steels

Hall, J. N., 2011, “Evolution of Advanced High Strength Steels in Automotive Applications”,

presented in Great Designs in Steel Seminar, May 18th, 2011

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Fundamental Requirement of Gen3 Steel

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• DP (Dual Phase) steels are a mixture of ferrite

and martensite. First generation.

• Strength from martensite

• TE from ferrite

DP Steels

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• TRIP (Transformation Induced Plasticity) Steels

• High end of First Generation Steels

• When deformed (in use) austenite transforms to

martensite increasing plastic behavior thus increasing

toughness

Steels with Retained Austenite

D.K. Matlock and J.G. Speer, “Design Considerations for the Next Generation of Advanced High Strength Sheet Steels,”

Proceedings of the The 3rd International Conference on Structural Steels, 2006, pp. 774-781.

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• Q&P steels concept developed by ASPPRC.

• Processing to increase retained austenite.

• Reported: 1500 MPa, 17% TE

Quench and Partitioned (Q&P) Steels

D.K. Matlock, V.E. Bräutigam, and J.G. Speer, “Application of the Quenching and Partitioning (Q&P) Process to a

Medium-Carbon, High-Si Microalloyed Bar Steel,” Proceedings of Thermec’2003, Trans Tech Publications, Inc,

Uetikon-Zurich. Switzerland, 2003, pp. 1089-1094.

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• TBF (TRIP aided Bainitic Ferrite) Steels

• Interrupted Austempering process

• Prior forging enhances properties

• Reported:

• 1000 MPa

• 30% TE

TBF Steels

B. C. De Cooman, “Structure–Properties Relationship in TRIP Steels Containing Carbide-Free Bainite,”

Current Opinion in Solid State and Materials Science, vol. 8, pp. 285–303, 2004.

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Q&P and TBF steels

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• Laboratory steels (not production).

• Research work to date has focused on sheet

steels with lower C content than most forging

steels.

• TE is not toughness, but a rough indication.

• Production runs of:

• QP980 980 MPa 20% TE

• QP1180 1180 MPa 14% TE

Caveats

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• These sheet steel compositions not yet ready for

many forging applications.

• The idea of having retained austenite to

increase strength and improve toughness is key.

Forging Outlook

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• To get retained austenite need careful control of

post forging heat treatment.

• Can be done in heat treat shop after forging, but

there would be added expense.

• Like microalloyed forging steels, control of time

and temperature directly off the press should be

considered.

Forging Outlook

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• Development of appropriate steel chemistries.

• Post forging time temperature control

• Continuous heat treatment conveyors?

• Forgings are thicker than sheet. Heat extraction?

• Precise timing needed.

• Effective quenching needed.

• Many research and technical details to be

resolved before actual implementation.

Challenges

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• Many new sheet steel (concepts) developed to

increase strength and TE (toughness)

• DP, TRIP, Q&P, TBF

• Not yet ready for forging applications

• These concepts (production schemes) may be

coming to the forging industry.

• Will require precise time and temperature

control post forging.

Conclusions

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Thank You