LIU Ji-yuan
,
ZHANG Zi-cheng
,
ZHU Fu-xian
,
LI Yan-mei
,
Manabe Ken-ichi
钢铁研究学报(英文版)
The controlled cooling technology following hot rolling process is a vital factor that affects the final microstructure and mechanical properties of the hot-rolled transformation induced plasticity (TRIP) steels. In the present study, low alloy C-Si-Mn TRIP steel was successfully fabricated by hot rolling process with a 450 hot rolling mill. To maximize the volume fraction and stability of retained austenite of the steel, two different cooling methods (air-cooling and ultra-fast cooling “AC-UFC” and ultra-fast cooling, air-cooling and ultra-fast cooling “UFC-AC-UFC”) were conducted. The effects of the cooling method on the microstructure of hot-rolled TRIP steel were investigated via optical microscope, transmission electron microscope and conversion electron Mssbauer spectroscope. The mechanical properties of the steel were also evaluated by conventional tensile test. The results indicated that ferrite and bainite in the microstructure were refined with the cooling method of UFC-AC-UFC. The morphology of retained austenite was also changed from small islands distributing in bainite district (obtained with AC-UFC) to granular shape locating at the triple junction of the ferrite grain boundaries (obtained with UFC-AC-UFC). As a result, the TRIP steel with a content of retained austenite of 1152%, total elongation of 32% and product of tensile strength and total elongation of 27552 MPa·% was obtained.
关键词:
hot-rolled TRIP steel
,
retained austenite
,
TRIP effect
,
Mssbauer spectra
,
mechanical property
ZHANG Ming-ya
,
ZHU Fu-xian
,
ZHENG Dong-sheng
钢铁研究学报(英文版)
Through the comparison of microstructure for polygonal ferrite (PF) matrix transformation induced plasticity (TRIP) seamless steel tube at different positions before and after tensile rupture, the transformation behavior of retained austenite (RA) was studied. The results showed that there were no yield points in tensile process and the splendid elongation and tensile strength were contributed by the uniform ferrite/bainite grains and the transformation of RA. The stability of RA was to some extent in inverse proportion with the ability of transformation induced plasticity. The coarse retained austenite located in ferrite and ferrite/bainite laths were all transformed into martensite during the tensile process.
关键词:
TRIP steel
,
retained austenite
,
austempering
,
heat treatment
张明亚
,
朱伏先
,
段争涛，曾周燏
钢铁
研究了冷轧退火马氏体基体TRIP钢在不同预拉伸过程中残余奥氏体向马氏体的转变。为了使残余奥氏体转变充分，试验拉伸速度设定为1mm/min。对不同变形条件下的试样进行分析,通过XRD分析残余奥氏体转变的体积分数及残余奥氏体中的碳浓度，通过SEM观察拉伸断裂后的断口形貌。分析发现：残余奥氏体转变过程与应力-应变有十分密切的关系，在变形的初始阶段和试样断裂之前，残余奥氏体的转变率较均匀变形阶段要小很多；在均匀变形阶段，即在出现颈缩之前，残余奥氏体发生稳定的马氏体相变，其转变率达到最大值，此时可以有效地提高均匀伸长率；在出现颈缩之后，残余奥氏体继续发生马氏体转变，但其转变率要较均匀转变时稍低。在整个变形过程中，残余奥氏体中的碳浓度呈线性增加。在变形的始末，虽然是应力-应变的最大梯度，但奥氏体的转变率并不是最高，反而为最低。
关键词:
退火马氏体基体
,
retained austenite
,
transformation
,
tensile process
