Papers in JOURNAL OF THE JAPAN SOCIETY FOR TECHNOLOGY OF PLASTICITY
(Vol.40 No.467 December 1999)
Effects of Lubrication on Accumulative Roll-Bonding (ARB) of Aluminum
Hiroshi UTSUNOMIYA, Koji TANDA, Yoshihiro SAITO,
Tetsuo SAKAI and Nobuhiro TSUJI
(Received on April 8, 1999)
The authors propose a novel, intense plastic forming, accumulative roll bonding (ARB), in order to produce
ultrafine grain materials with very high strength. The effects of lubrication on the ARB process of commercial
aluminum I 100 at 473K are investigated in this study. Under unlubricated conditions, severe redundant shear
strain is introduced by the friction between the roll and the material. The attained strength of the unlubricated
materials is much higher than that of the oil-lubricated materials. The unlubricated materials show an ultrafine
grain structure. On the other hand, the lubricated materials show a subgrain structure. In the unlubricated
materials, the shear texture is well developed near the surface, due to friction, while the rolling texture is weak
in the center of thickness. It is assumed that the redundant shear strain is very effective for obtainig ultrafine
grain, and high-strength materials using the ARB process.
Key words : accumulative roll-bonding, ARB, ultrafine grain, supermetal, lubrication, rolling, aluminum,
intense plastic forming
Highly Tensile and Ductile Steel Containing Ultrafine-Grained
Ferrite Formed in Wire Rod Rolling
- Control Technology of Microstructure in Wire Rod and Bar Rolling I -
Yukio NOGUCHI and Hiroshi YADA
(Received on May 20, 1999)
In order to utilize the toughening effect, which was expected based on the formation of ultrafine-grained
ferrite during high-temperature deformation, 0.20~0.29 mass%C steels were hot-rolled using an experimental
wire rod mill, and their mechanical properties and microstructure were studied. The main results are as
follows. (1) When finish-rolled at 900 to 950 Celsius (above their A3) and rapidly quenched, they showed good
toughness (reduction of area) and ductility at tensile strength 1500 to 2000MPa. Their microstructure
contained less than 3 to 5- of ultrafine-grained ferrite surrounded by martensite whose lath length was
reduced to under 10 micro meter compared with the above 40 micro meter in undeformed specimens which showed lower tensile
strength and toughness than the above materials. This shortening of martensite lath by ultrafine-grained ferrite
was surmised to be the cause of toughening. TEM observation showed that the ferrite grains were polygonal
and 0.7~1 micro meter by 0.3~0.5 micro meter in size. (2) When finishing temperature was lowered to below 900 Celsius, the size
and the quantity of ferrite increased, and both tensile strength and toughness decreased.
Key words : thermomechanical heat treatment, ultrafine-grained ferrite, low-carbon steel, wire rod and bar
rolling, continuous rolling, mechanical properties