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PROTEC127781-10
Journal of Materials Processing Technology xxx (2010) xxx-xxx
1 1.
Contents lists available at ScienceDirect
Journal of Materials Processing Technology
journal homepage: www.elsevier.com/locate/jmatprotec
1 Effect of forging strain rate and deformation temperature on the mechanical
2 properties of warm-worked 304L stainless steel
3 N.T. Switznera, C.J. Van Tyneb*, M.C. Matayab
4 a Honeywell Federal Manufacturing & echnologies, 2000 E. Bannister Rd, Kansas City, MO 64141, SA
5 b Department of Metallurgical and Mdrials Engineering, Colorado School of Minesg20 15th St, den, CO 80401-1887, USA
7 A R T I C L E IN F O
8
9 Article history:
10 Received 12 August 2009
11 Received in revised form
12 14 November 2009
13 Accepted 19 January 2010
Available online xxx
14
15 Keywords:
16 Warm working
17 train rate
18 eformation temperature
19 Mechanical properties
A B S T R A C T
Stainless steel 304L forging were produced with four different types of production forging quipment
- hydraulic press, mechanical press, screw press, and high-energy rate forging (HERF). EatN machine
imparted a different nominal strain rate during the deformation. The final forgings were done at the
warm working (low hot working) temperatures of 816 C, 843 C, and 871 C. The objectives of the study
were to characterize and understand the effect of industrial strain rates (i.e. processing equipment), and
deformation temperature on the mechanical properties for the final component. Some of the compo-
nents were produced with an anneal prior to the final forging while others were deformed without the
anneal. The results indicate that lower strain rates produced lower strength and higher ductility com-
ponents, but the lower strain rate processes were more sensitive to deformation temperature variation
and resulted in more within-part property variation. The highest strain rate process, HERF, resulted in
slightly lower yield strength due to internal heating. Lower processing temperatures increased strength,
decreased ductility but decreased within-part property variation. The anneal prior to the final forging
produced a decrease in strength, a small increase in ductility, and a small decrease ofwithin-part property
variation.
2010 Published by Elsevier B.V.
20 1. Introduction
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During forging processes, dynamic and interconnected vari-
ables, such as strain, strain rate, strain distribution, temperature,
and cooling rate control how the microstructure evolves. Altan et
al. (1973) indicated the importance of deformation temperature by
stating that above the ecrystallization temperature of a formed
metal, strain rate is the significant processing parameter, while
below the recrystallization temperature, strain is the processing
parameter of primary significance. Hertzberg (1996) defines metal
deformation above the recrystallization temperature as hot work-
ing. McQueen (1977) revealed that for many metals there is also
a transitional region of forming temperatures between hot work-
ing and cold working within which both strain, and strain rate
as well as deformation temperature interact to affect the result-
ing microstructure and mechanical properties. This intermediate
temperature range is often called the warm working range. The
deformation temperatures for 304L stainless steel in the present
study are in this range.
* Corresponding author. Tel.: +1 303 273 3793; fax: +1 303 273 3795.
E-mail address: cvantyne@mines.edu (CJ. Van Tyne).
1.1. Effects ofkmperature and strain rate
There have been previous studies on the deformation of 304L
austenitic stainless steel in the warm working range but with
a limited number of strain rates. Mataya et al. (1981) showed
that for 21-6-9 and 304L deformed at high strain rate of approx-
imately 800s-, there is an increase in the warm/hot working
transition temperature up to at least 60% of the absolute melt-
ing point of the alloy. They used high-energy rate forging (HERF)
equipment to produce several complex geometries in temperatures
ranging from 760 C to 955 C and found deformation tempera-
ture and geometry affect the final mechanical properties of the
parts. Mataya et al. (1981) also observed large microstructural
and hardness variations across parts forged in this temperature
range.
Mataya et al. (1990) performed forward extrusion tests on
cylindrical 304L specimens by HERF and press forming. In their
experiments, HERF and press forming strain rates for the specific
geometry were approximately 2000s- and 2s-1, respectively.
Contour maps were created for the estimated 0.2% offset yield
strength as a function of forging temperatures from 600 C to
1200 C and percent reduction up to 80%. These contour plots, how-
ever, lacked the necessary detail to estimate yield strength for
production forgings at intermediate strain rates and at common
production forging temperatures.
0924-0136/$ - see front matter 2010 Published by Elsevier B.V.
doi:10.1016/j.jmatprotec.2010.01.014
Please cite this article in press as: Switzner, N.T., et al., Effect of forging strain rate and deformation temperature on the mechanical properties
of warm-worked 304L stainless steel. J. Mater. Process. Tech. (2010), doi:10.1016/j.jmatprotec.2010.01.014
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