WANG Qingfeng
,
CHAI Feng
,
CAI Jianwei
,
PAN Tao
,
SU Hang
钢铁研究学报(英文版)
The kinetics of εCu particle dissolution in the matrix of heat affected zone (HAZ) during welding of a coppercontaining steel was determined by assembling the welding temperaturetime program into a modified Whelan′s solution. The particle dissolution dependence on the degree of “superheating” above the equilibrium transformation is demonstrated from the model. In terms of volume fraction of particle dissolution, the HAZ may be classified into three zones, including the undissolving zone, the partially dissolving zone, and the completely dissolving zone, respectively. The numerical solution was in good agreement with the experimental examination finding. The results of model can be used to quantitatively map the εCu dissolution zone dependence on the peak temperature of welding thermal cycles and understand the evolution of this transformation during welding.
关键词:
εCu;particle dissolution;kinetics;welding;steel
LUO Zhi-jun
,
SHEN Jun-chang
,
SU Hang
,
et al
钢铁研究学报(英文版)
Substructure of M/B mixed structure in a low carbon NiCrMoV steel obtained through different cooling mode were quantitative analysis by optical microscope, SEM, EBSD and TEM to investigate the effect of the substructure on toughness. The results indicated that with the same prior austenite grain size and mixed by different ratio of M and B, toughness of steel enhanced with decrease of packet and block size and the lath width was about 0.38um. Calculation showed that packet and block boundary have the same effect on delaying crack extension, furthermore, effect of block width on impact energy was notably bigger than packet one. Therefore, block could work as a contributing microstructure controlled substructure in low carbon martensite steels, which means that block size was “the effect grain size controlling toughness”.
关键词:
lath martensite/bainite mixed structure;toughness;EBSD;crack extension
CHAI Feng
,
YANG Caifu
,
SU Hang
,
ZHANG Yongquan
,
XU Zhou
钢铁研究学报(英文版)
The weldability of a lowcarbon copperbearing age hardening steel was evaluated using cracking susceptibility calculation, HAZ maximum hardness measurement, and Ygroove cracking evaluation test. The results show that the hardenability characteristics and cold cracking susceptibility of the steel are very low. The results also indicate that a crackfree weldment can be obtained during the welding of this type of steel even at an ambient temperature as low as -5 ℃ as well as in an absolute humidity lower than 4 000 Pa without any preheat treatment. A slight preheat treatment can prevent the joint from cracking when welding is carried out at lower ambient temperature or higher absolute humidity.
关键词:
copperbearing age hardening steel;weldability;cracking resistance;Ygroove cracking test
SU Hang
,
PAN Tao
,
LI Li
,
YANG Caifu
,
CUI Yinhui
,
JI Huaizhong
钢铁研究学报(英文版)
By combining thermomechanical coupling finite element analysis with the characteristics of phase transformation [continuous cooling transformation (CCT) curve], the thermal fatigue behavior of train wheel steel under high speed and heavy load conditions was analyzed. The influence of different materials on the formation of the phase transformation zone of the wheel tread was discussed. The result showed that the peak temperature of wheel/track friction zone could be higher than the austenitizing temperature for braking. The depth of the austenitized region could reach a point of 09 mm beneath the wheel tread surface. The supercooled austenite is transformed to a hard and brittle martensite layer during the following rapid cooling process, which may lead to cracking and then spalling on the wheel tread surface. The decrease in carbon contents of the train wheel steel helps inhibit the formation of martensite by increasing the austenitizing temperature of the train wheel steel. When the carbon contents decrease from 07% to 04%, the Ac3 of the wheel steel is increased by 45 ℃, and the thickness of the martensite layer is decreased by 30%, which is helpful in reducing the thermal cycling fatigue of the train wheel tread such as spalling.
关键词:
train wheel steel;thermal cycling fatigue;friction;martensite transformation;thermomechanical coupling
ZHAO Xiqing
,
PAN Tao
,
WANG Qingfeng
,
SU Hang
,
YANG Caifu
,
YANG Qingxiang
钢铁研究学报(英文版)
Mechanical properties of quenching, intercritical quenching and tempering (QLT) treated steel containing Ni of 9% were evaluated from specimens subject to various tempering temperatures. The detailed microstructures of steel containing Ni of 9% at different tempering temperatures were observed by optical microscope (OM) and transmission electron microscope (TEM). The volume fraction of austenite was estimated by XRD. The results show that high strength and cryogenic toughness of steel containing Ni of 9% are obtained when the tempering temperature are between 540 and 580 ℃. The microstructure keeps the dual phase lamellar structure after the intercritical quenching and there is cementite created in the Nirich constituents when tempering temperature is 540 ℃. When tempering temperatures are between 560 and 580 ℃, the reversed austenites (γ′) grow up and the dual phase lamellar structure is not clear. The γ′ becomes instable at 600 ℃. When tempered at temperature ranging from 500 to 520 ℃, the increase of dislocation density in the lamellar matrix makes both tensile strength and yield strength decrease. When tempered at 540 ℃ and higher temperature, the yield strength decreases continuously because the C and alloying elements in the matrix are absorbed by the cementite and the γ′, so the yield ratio is decreased by the γ′. There are two toughness mechanisms at different tempering temperatures. One is that the precipitation of cementite absorbs the carbon in the steel which plays a major role in improving cryogenic toughness at lower temperature. Another is that the γ′ and the purified matrix become major role at higher tempering temperature. When the tempering temperature is 600 ℃, the stability of γ′ is decreased quickly, even the transformation takes place at room temperature, which results in a sharp decrease of CharpyV impact energy at 77 K. The tempering temperature range is enlarged by the special distribution of cementite and the lamellar structure.
关键词:
steel containing Ni of 9%
,
tempering temperature
,
cementite
,
reversed austenite
,
cryogenic toughness
CHAI Feng
,
YANG Caifu
,
SU Hang
,
ZHANG Yongquan
,
XU Zhou
钢铁研究学报(英文版)
Effects of Mg on the chemical component and size distribution of Tibearing inclusions favored grain refinement of the welding induced coarsegrained heat affected zone (CGHAZ), with enhanced impact toughness in Tikilled steels, which were examined based on experimental observations and thermodynamic calculations. The results indicated that the chemical constituents of the inclusions gradually varied from the TiO+TiMgO compound oxide to the TiMgO+MgO compound oxide and the singlephase MgO, as the Mg content increased from 0002 3% to 0006%. A trace addition of Mg (approximately 0002%) led to the refinement of Tibearing inclusions by creating the TiMgO compound oxide and provided favorable size distribution of the inclusions for acicular ferrite transformation with a high nucleation rate in the CGHAZ, and a high volume fraction of acicular ferrite was obtained in the CGHAZ with enhanced impact toughness. Otherwise, a high content of Mg (approximately 0006%) produced a singlephase MgO, which was impotent to nucleate an acicular ferrite, and a microstructure comprised of a ferrite side plate and a grain boundary ferrite developed in the CGHAZ. The experimental results were confirmed by thermodynamic calculations.
关键词:
nonmetallic inclusion;magnesium;acicular ferrite;coarsegrained heat affected zone (CGHAZ)
陆振华
,
许宝建
,
金庆辉
,
赵建龙
功能材料与器件学报
doi:10.3969/j.issn.1007-4252.2008.03.015
PDMS是制作微流控芯片的主要材料.PDMS芯片制作的主要方法是模塑法,模塑法要求有良好的塑性成型模具.SU-8以其良好的微加工特性,目前已广泛应用于微机械结构的制作,也用于PDMS塑性成型的模具.本文根据模具的特殊性,如平整、无裂纹、可多次使用等要求,研究了影响SU-8模具结构与基底材料硅片的黏附性和形成裂纹的因素,优化了SU-8微模具加工工艺,在以0.5℃/min进行升降温、210 mJ/cm2的曝光剂量、200℃条件下硬烘30min条件下得到较好的SU-8模具,提供了一种快速、复用性高、低成本的PDMS微芯片塑性成型的SU-8模具的制作方法.
关键词:
PDMS
,
塑性成型
,
SU-8模具
,
黏附性
刘俊
,
常梦洁
,
杜慧玲
高分子材料科学与工程
doi:10.16865/j.cnki.1000-7555.2016.04.023
利用静电纺丝和紫外光刻技术直接制备了不同结构的SU-8光刻胶纳米纤维薄膜及图案阵列.通过光学显微镜和扫描电子显微镜表征了纳米纤维的形貌、尺寸及结构.结果表明,通过改变SU-8光刻胶的黏度可形成不同直径和形貌的纤维结构,其中用SU-8 3010和SU-8 3050光刻胶制备的纳米纤维具有最优的形貌,其平均直径分别为470 nm和610nm.利用带有长方形缺口的铝箔和同轴电纺的方法分别制备了平行趋向和空心结构的纳米纤维.通过紫外光刻过程,可将SU-8纳米纤维加工成点阵、条状等不同形貌的图案阵列或结构,有望用作细胞培养研究的功能基底材料.
关键词:
静电纺丝
,
纳米纤维
,
SU-8光刻胶
,
纤维图案
张金娅
,
陈迪
,
朱军
,
李建华
,
方华斌
,
杨斌
功能材料与器件学报
doi:10.3969/j.issn.1007-4252.2005.02.027
采用新型SU-8光刻胶在UV-LIGA技术基础上制备了各种高深宽比MEMS微结构,研究了热处理和曝光两个重要因素对高深宽比微结构的影响,解决了微结构的开裂和倒塌等问题;优化了SU-8胶工艺,从而获得了最大深宽比为27:1的微结构.
关键词:
UV-LIGA技术
,
SU-8胶
,
高深宽比微结构
