材料期刊网

Fatigue Properties of Supersteel for Automobiles

DU Linxiu , ZHANG Zhongping , TIAN Yuwei , LIU Xianghua , WANG Guodong

钢铁研究学报(英文版)

gy Center, Benxi Steel Group, Benxi 117000, Liaoning, China)
Abstract： The fatigue properties of 400 MPa grade supersteel, plain low carbon steel SS400 and microalloyed steel Q340TM were investigated through tensilecompression fatigue experiment with R=-1. The results indicate that the fatigue limit of the 400 MPa supersteel is higher than that of SS400 steel and close to that of the 340TM steel. According to the analysis of fatigue fracture, the fatigue striations of supersteel SS400 is thinner than that of SS400 steel and 340TM steel, and grain refinement can increase the fatigue limit.

关键词: supersteel;grain refinement;fatigue property

Effect of Thermomechanical Processing on Microstructures of TRIP Steel

TANG Zhengyou , DING Hua , DU Linxiu , 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 hotrolled transformationinduced 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, carbidefree bainite and retained austenite were determined. With increasing the hot deformation amount and the ferrite content and decreasing the carbidefree 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

Fatigue Property of Low Cost and High Strength Wheel Steel for Commercial Vehicle

WANG Ning , LI Yi , DU Linxiu , WU Di , LIU Xianghua

钢铁研究学报(英文版)

The fatigue properties of the newly developed wheel steel used for commercial vehicles were studied using pushpull axial loading fatigue tests with stress ratio R=-1. Q235B steel, which is conventionally applied to commercial vehicle wheels, was also analyzed for comparison. Although the chemical composition and microstructure (ferrite and pearlite) of newly developed wheel steel were similar to those of Q235B, the 107 cycles fatigue limit of the new wheel steel was 260 MPa, which is 24% higher than that of Q235B (210 MPa). The improvement of the fatigue strength of the new wheel steel can be attributed to grain refinement. In order to investigate the effect of the decrease in thickness of the wheel steel on the fatigue property of the wheel, dynamic cornering fatigue tests were conducted on full scale wheels with the model of 825×225. The results indicated that the newly developed wheel steel had outstanding fatigue life even if the mass loss was 10% in comparison with Q235B.

关键词: high strength wheel steel;fatigue strength;grain refinement;dynamic cornering

Microstructure Evolving Behaviors of Undercooled Ultrafine Austenite Grains During Deformation

YAO Shengjie , DU Linxiu , LI Guanglong , JIAO Xing , WANG Guodong

钢铁研究学报(英文版)

Samples with ultrafine grained austenite were prepared by repetitive rapid heating and quenching for three times and were used to investigate the dynamic microstructural evolving behaviors at different temperatures. A simultaneous development of dynamic straininduced transformation (DSIT) and austenite grain growth was detected at the deformation temperatures above Ar3, while only DSIT happened as the deformation proceeded at lower temperatures close to and below Ar3. In addition, a reverse ferritetoaustenite transformation was also observed. Most of the straininduced ferrite nucleated on the boundaries of ultrafine prior austenite grains, especially at the corners and no evidence about intragranular nucleus was obviously obtained.

关键词: ultrafine grained austenite , ferrite , dynamic straininduced transformation (DSIT) , grain growth

Effect of WarmRolled Pearlite Microstructural Features on Austenitic Transformation

YAO Shengjie , DU Linxiu , LIU Xianghua , WANG Guodong

钢铁研究学报(英文版)

The austenite transformation characteristics for various warmrolled pearlite during rapid heating were investigated. The results indicate that the start temperature (Ts) is sensitive to the microstructural feature of pearlite, whereas the dislocation plays an important role in the transformation rate; at the same time, the uniformity of austenite grains is more or less affected by the amount of spheroidized pearlite. A critical effect on the state of austenite grain is created through the influence of initial microstructures on the start temperature of transformation.

关键词: warm rolling;pearlite;dislocation;austenite;transformation

Development of NbVTi HotRolled High Strength Steel With Fine Ferrite and Precipitation Strengthening

YI Hailong , DU Linxiu , WANG Guodong , LIU Xianghua

钢铁研究学报(英文版)

A hotrolled steel with high yield strength of 700 MPa, good elongation of about 20% and low ductilebrittle transition temperature (DBTT) lower than -70 ℃ has been developed in laboratory. The results show that adopting finishing rolling temperature of around 800 ℃ is rational, and coiling temperature is between 400 and 500 ℃. The strength of developed 700 MPa hotrolled high strength steel is derived from the cumulative contribution of fine grain size, dislocation hardening and precipitation hardening. The fine grain strengthening and precipitation hardening are the dominant factors responsible for such high strength, and good elongation and toughness are predominantly due to fine grain ferrite.

关键词: high strength steel;precipitation hardening;ductilebrittle transition temperature;fine grain strengthening

Dynamic and Static Recrystallization Behavior of Low Carbon High Niobium Microalloyed Steel

LAN Liangyun , QIU Chunlin , ZHAO Dewen , GAO Xiuhua , DU Linxiu

钢铁研究学报(英文版)

The recrystallization behavior of a low carbon high Nb microalloyed steel was investigated using Continuous and interrupted hot compression tests. The results showed that the onset of dynamic recrystallization (DRX) could be detected from inflection in the plot of the strain hardening rate θ against stress σ regardless of whether the stress peak appears or not. According to Zener-Hollomon parameter the activity energy of DRX (Qdef) was obtained, and a new modified expression calculating Qdef was proposed in consideration of the chemical composition of experimental steel. Applying the 2% offset method the static softening fraction was determined. The graphic representation of the softening fraction vs. interrupt time gave the information of the non-static recrystallization temperature (about 1000℃)and the relationship of precipitation-time-temperature. Static recrystallization kinetics follow Avrami’s law in high deformation temperature, and different values of the exponent n were given to illustrate the different effects of Nb element on static recrystallization at different deformation temperature.

关键词: dynamic recrystallization;static recrystallization;high Nb microalloyed steel;activity energy.

Transformation Behavior of Low Carbon Steels Containing Two Different Si Contents

CAI Minghui , DING Hua , ZHANG Jiansu , LI Long , LI Xiaobin , DU Linxiu

钢铁研究学报(英文版)

Continuous cooling transformation behaviors of low carbon steels with two Si contents (050% and 135%) 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 04, 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

DU-Ti合金表面N+Ti+多层Ti/TiN复合膜的制备与耐蚀性

严东旭 , 刘天伟 , 龙重 , 白彬 , 张鹏程 , 黄河 , 郎定木 , 王晓红 , 朱建国

材料保护

采用单一的表面改性技术难以提高贫铀钛合金(Du-Ti)的耐蚀性能.采用等离子体浸没离子注入技术依次在Du-Ti合金表面注入N和Ti,再利用非平衡脉冲磁控溅射技术制备多层Ti/,TiN,研究了膜层的形貌、结构及耐蚀性能.结果表明:膜层厚约3μm,呈柱状结构,致密,但存在一些微缺陷,膜基结合紧密;膜层出现面心立方结构的TiN和密排六方的Ti,在DU-Ti合金界面形成了少量的UO2,没有铀的氮化物;膜层耐蚀性能较基体得到较大提高;微观缺陷是TiN层局部片状脱落的主要原因,外层TiN出现片状脱落后.注入层和内层Ti/TiN多层膜仍能有效保护基体.

关键词: 等离子体浸没离子注入 , 非平衡磁控溅射 , 复合膜 , DU-Ti合金 , 电化学腐蚀 , 耐蚀性

Du Pont推出全新应用的聚烯烃弹性体

合成材料老化与应用

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