WANG Qian
,
WANG Jian
,
WENG Xiaojun
,
SUN Jian
,
CHEN Shipu
,
HU Gengxiang (Shanghai Jiaotong University
,
Shanghai 200010. China)
金属学报(英文版)
To explore the approaches of combined toughening and strengthening of the Al_3Ti-based L1_2 intermetallic alloys, multiphase Al_3Ti alloys formed by combining with reinforcement or by second phase precipitation are being studied. The interface reactions between Al_(66)Fe_9Ti_(25)matrix and SiC reinforcement were investigated. It is determined that SiC is chemically incompatible with the Al_(66)Fe_9Ti_(25)matrix, Al_2O_3 barrier coating on SiC by sol-gel process was developed to minimize the interfacial reactions. On the other hand, a new type of Al_3Ti-based alloy having a L1_2 matrix with second phase precipitation has been developed. The quaternary alloys based on Al_(66)Fe_9Ti_(25)and modified with Nb additions, consist of a L1_2 matrix and D0_(22) second phase in the annealed state ,but the second phase can be dissolved by solution treatment and precipitated during high temperature aging.
关键词:
:Al_3Ti alloy
,
null
,
null
,
null
,
null
HE Sheng-ping
,
HUANG Qing-yun
,
ZHANG Guo-xing
,
LU Yong-jian
,
WANG Qian
钢铁研究学报(英文版)
In continuous casting of peritectic steel grades sensitive to longitudinal cracking, the solidification properties of mold fluxes play an important role in keeping smooth running of continuous casting process and achieving high surface quality of casting strands. To reduce fluorine pollution in molten slag, types of CaO-SiO2-TiO2 (CTS) based mold fluxes were investigated. The solidification and crystallization properties, including viscosity η at 1573 K, break temperature Tbr, crystallization ratio Rc and solidification mineragraphy were measured, which were compared with those of CaO-SiO2-CaF2 based mold fluxes. The experiments show that there are unstable viscosity-high temperature properties and high Tbr in part of CTS slag system, which are bad for lubrication between liquid flux film and strand. And when temperature is below Tbr, the viscosities change slowly during cooling in some part of this slag system, which imply that liquid mold fluxes solidify slowly and it is easy to cause surface longitudinal cracks on strand. Major mineragraphy of the CaO-SiO2-TiO2 based mold fluxes are CaO·TiO2 or CaO·TiO2 and CaO·SiO2·TiO2. TiN and Ti(C,N) can be formed in mold fluxes bearing high TiO2 during the continuous casting.
关键词:
mold flux
,
solidification property
,
peritectic steel
,
mineragraphy
LONG Xiao
,
HE Sheng-ping
,
XU Jian-fei
,
HUO Xu-ling
,
WANG Qian
钢铁研究学报(英文版)
In high speed continuous casting of peritectic steel slabs, mold fluxes with high basicity are required for less surface defect product. However, the basicity of remaining liquid slag film tends to decrease in casting process because of the crystallization of 3CaO·2SiO2·CaF2. Thus, a way is put forward to improve mold fluxes′ properties by raising the original basicity. In order to confirm the possibility of this method, the effect of rising original basicity on the properties of mold fluxes is discussed. Properties of high fluorine based mold fluxes with different basicities and contents of CaF2, Na2O, and MgO were measured, respectively. Then, properties of higher basicity mold fluxes were discussed and compared with traditional ones. The results show that increasing the basicity index can improve the melting and flow property of mold fluxes. With the increasing basicity, crystallization rate of mold fluxes increases obviously and crystallization temperature tends to decrease when the basicity exceeds 1.35. The method presented before is proved as a potential way to resolve the contradiction between horizontal heat transfer controlling and solidified shell lubricating for peritectic steel slab casting. But further study on improving the flow property of liquid slag is needed. This work can be used to guide mold fluxes design for high speed continuous casting of peritectic steel slabs.
关键词:
mold flux
,
high basicity
,
crystallization property
,
peritectic steel
ZHENG Lei
,
YUAN Ze-xi
,
SONG Shen-hua
,
XI Tian-hui
,
WANG Qian
钢铁研究学报(英文版)
Austenite grain sizes in the heat affected zone (HAZ) of a high heat input welded Zr-Ti bearing microalloyed steel are measured under different welding conditions simulated by a Gleeble-1500 thermal-mechanical simulator. The austenite grain growth is divided into two regimes in terms of temperature. When the temperature is lower than 1250 ℃ where the pinning effect of precipitates is strong, the austenite grain size increases slowly with increasing peak temperature, but it increases drastically when the temperature is higher than 1250 ℃ where the pinning effect of precipitates is weak. Based on the experimental measurements, an analytical model for predicting the austenite grain size in the heat affected zone is derived. Model predictions indicate that the initial grain size has little effect on the final one, and the grain growth depends mainly on heat input and peak temperature as well as growth activation energy and exponent. With the use of the model, the width of coarse grained heat affected zone (CGHAZ) for a thick plate is predicted.
关键词:
welding
,
high heat input
,
microstructure
WANG Qian
,
LU Yongjian
,
HE Shengping
,
WANG Lijuan
,
K C Mills
钢铁研究学报(英文版)
Excessive sintering of mould fluxes can readily cause defects and sticker breakouts in continuously cast strands. Studying the sintering property is important to minimize problems related to sintering arising from the use of mould fluxes in continuous casting. An effective method of measuring the apparent sintering temperature has been developed in this study. The method is based on monitoring the formation of cavities caused by melting of samples. For monitoring, the differential pressure of an inert gas flow was measured through a set volume of sample (mould flux A) held in a furnace tube. The apparent sintering temperature was defined in this test to determine sintering process. The sintering properties of fluxes with various contents of carbon black were examined along with identification of mineralogical phases and the nature of the sinter for samples of mould flux A held for one hour at different temperatures. The experimental results indicated that the apparent sintering temperature (AST) was a useful parameter to assess the threat of problems related to sinter.
关键词:
mould flux; sintering property; differential pressure; apparent sintering temperature
