DING Hua
,
LI Hua-ying
,
DING Hao
,
QIU Chun-lin
,
TANG Zheng-you
钢铁研究学报(英文版)
Two steels without and with Nb addition were chosen to investigate the effects of Nb on the microstructures and the mechanical properties of Fe-Mn-Al-Si steels. The results revealed that Nb refined the grains markedly and both TRIP and TWIP effects occurred during deformation process. The Nb containing steel possesses higher yield strength and much lower tensile strength, the latter being explained by the suppression of TRIP effect due to the increase of stacking fault energy. This indicates grain refining is secondary for strengthening of steels when TRIP or TWIP effect exists during the deformation of low carbon and high Mn steels.
关键词:
grain size
,
strength
,
high Mn steel
,
Nb
TANG Zhengyou
,
DING Hua
,
DU Linxiu
,
DING Hao
,
ZHANG Xin
钢铁研究学报(英文版)
In order to control retained austenite, the effect of hot deformation in the intercritical region on the microstructure of hotrolled transformationinduced plasticity (TRIP) steel was studied on a Gleeble 1500 hot simulator. Compressive strains varying in amounts from 0 to 60% were imposed in the intercritical region, and effects on the formation of polygonal ferrite, carbidefree bainite and retained austenite were determined. With increasing the hot deformation amount and the ferrite content and decreasing the carbidefree bainite content, the volume fraction of retained austenite decreases. Increased dislocation density, grain refinement of ferrite and carbon enrichment are the main factors which control retained austenite stability.
关键词:
TRIP steel;intercritical (α+γ) region;hot deformation;retained austenite
DING Hua
,
TANG ZhengYou
,
LI Wei
,
WANG Mei
,
SONG Dan
钢铁研究学报(英文版)
The mechanical properties and microstructure of two low carbon high manganese steels with 238% (No1) and 33% (No2) (mass percent) of manganese were investigated. The results showed that No1 steel possesses high strength and high plasticity, and No2 steel has a relatively high strength and extraordinary plasticity. The No1 steel exhibits both TRIP (transformation induced plasticity) and TWIP (twin induced plasticity) effects during the deformation; while only TWIP effect appeared under the same deformation condition for No.2 steel. The comparison between the microstructures and mechanical properties of two steels was made, and the strengthening mechanisms were also analyzed.
关键词:
manganese;TRIP;TWIP;microstructure;mechanical property
DING Hao
,
DING Hua
,
QIU Chunlin
,
TANG Zhengyou
,
ZENG Jianmin
,
YANG Ping
钢铁研究学报(英文版)
The mechanical property and forming limit experiments were carried out on a high manganese TRIP/TWIP steels with 18.8% manganese. And the forming limit diagram was obtained. This high manganese steel shows outstanding mechanical properties combining high strength and good formability. Its FLD0 is about 38%. The effects of conventional mechanical property on the FLD0 were analyzed. With the contents of Mn increasing, FLD0 increases, which indicates TWIP effect is advantageous to enhance formability. Combining with three classical models and volume invariable principle, a FLD model was established, which fits high manganese steels very well.
关键词:
high manganese TRIP/TWIP steel;mechanical properties;formability;forming limit diagram
CAI Minghui
,
DING Hua
,
ZHANG Jiansu
,
LI Long
,
LI Xiaobin
,
DU Linxiu
钢铁研究学报(英文版)
Continuous cooling transformation behaviors of low carbon steels with two Si contents (050% and 135%) were investigated under undeformed and deformed conditions. Effects of Si contents, deformation, and cooling rates on γ transformation start temperature (Ar3), phase microstructures, and hardness were studied. The results show that, in the case of the deformation with the true strain of 04, the length of bainitic ferrite laths is significantly decreased in low Si steel, whereas, the M/A constituent becomes more uniform in high Si steel. An increase in cooling rates lowers the Ar3 greatly. The steel with higher level of Si exhibits higher Ar3, and higher hardness both under undeformed and deformed conditions compared with the steel with a lower Si content. Especially, the influence of Si on Ar3 is dependent on deformation. Such effects are more significant under the undeformed condition. The hardness of both steels increases with the increase of cooling rates, whereas, the deformation involved in both steels reduces the hardness.
关键词:
Si content;low carbon steel;cooling rate;transformation behavior;bainitic