WANG Jin
,
CHEN Jun
,
ZHAO Zhen
,
RUAN Xueyu
钢铁研究学报(英文版)
The dynamic recrystallization behavior of microalloyed forged steel was investigated with a compression test in the temperature range of 1 223-1 473 K and a strain rate of 001-5 s-1. Activation energy was calculated to be 3059 kJ/mol by regression analysis. Modeling equations were developed to represent the dynamic recrystallization volume fraction and grain size. Parameters of the modeling equations were determined as a function of the ZenerHollomon parameter. The developed modeling equation will be combined with finite element modeling to predict microstructural change during the hot forging processing.
关键词:
microalloyed forged steel;dynamic recrystallization;flow stress
ZHOU Guo-ping
,
LIU Zhen-yu
,
YU Shi-chuan
,
CHEN Jun
,
QIU Yi-qing
,
WANG Guo-dong
钢铁研究学报(英文版)
The formation of phosphorous surface inverse segregation (SIS) in twin-roll cast strips of low-carbon steels was studied. High phosphorous strips were fabricated by using a pilot twin-roll strip caster and a melt/substrate contacting apparatus, respectively. Solidification structures of strips were observed and analyzed, and phosphorus distributions along longitudinal sections of strips were investigated and discussed. The results showed that solidification structures of all strips were columnar grains, either integrated or coarse in the strip made by the melt/substrate contacting apparatus or damaged in some degree in cast strips; and that during cast strip solidification, enrichment of phosphorus occurred between columnar grains, and the average phosphorus concentration near the surface in the strip with 015% of phosphorus was measured to be about 027% which was obviously higher than that in the bulk.
关键词:
strip casting
,
phosphorus enrichment
,
inverse segregation
,
steel
,
solidification
ZHOU Bin
,
SHEN Yu
,
CHEN Jun
,
CUI Zhenshan
钢铁研究学报(英文版)
The evolution of eutectic carbide in as-cast M2 high-speed steel on different deforming conditions was investigated. Initially, specimens were deformed by hot compression in the range of 1223 to 1398K at strain rates of 0.01 to 1.0s-1. In a series of continuous deformation tests the flow stress curves were determined for the downstream process simulation. Subsequently, metallographic examination was carried out before and after deformed specimens for carbides analysis. As-cast microstructure is characterized as a spherical matrix of austenite and a continuous network of rodlike or irregular eutectic carbide, whereas deformed microstructure has broken carbide network and smaller granular products on all experimental conditions. It suggests that eutectic carbides fracture to particles during hot deformation by thermomechanical disintegration, while diffusion-controlled phase transformation was not remarkable. Combination with numerical simulation, the relationship between breakdown ratio of carbide network and deforming parameters were concluded. Strain was the most important one to shatter eutectic carbides and disperse products. Furthermore, critical strain values were obtained, beyond which carbide network disappeared, and fractured carbides kept a stable profile and deformed with matrix coordinately. A higher temperature or lower strain rate resulted in a lower critical strain.
关键词:
hot compression;high-speed steel;eutectic carbide;breakdown mechanism
