G Subhash Chander
,
G Madhusudhan Reddy
,
A Venugopal Rao
钢铁研究学报(英文版)
Fundamental investigation of continuous drive friction welding of austenitic stainless steel (AISI 304) and low alloy steel (AISI 4140) is described. The emphasis is made on the influence of rotational speed on the microstructure and mechanical properties such as hardness, tensile strength, notch tensile strength and impact toughness of the dissimilar joints. Hardness profiles across the weld show the interface is harder than the respective parent metals. In general, maximum peak hardness is observed on the stainless steel side, while other peak hardness is on the low alloy steel side. A trough in hardness distribution in between the peaks is located on the low alloy steel side. Peak hardness on the stainless steel and low alloy steel side close to the interface increases with a decrease in rotational speed. All transverse tensile joints fractured on stainless steel side near the interface. Notch tensile strength and impact toughness increase with increase in rotational speed up to 1500 r/min and decrease thereafter. The mechanism of influence of rotational speed for the observed trends is discussed in the torque, displacement characteristics, heat generation, microstructure, fractography and mechanical properties.
关键词:
friction welding
,
dissimilar metal joint
,
austenitic stainless steel
,
low alloy steel
,
microstructure
,
impact toughness
,
tensile strength
CHEN Ai-hua
,
XU Jian-qiu
,
LI Ran
,
LI Hua-long
钢铁研究学报(英文版)
The mechanical properties, corrosion resistance and microstructures of high performance steel (HPS) was investigated by tensile testing machine, Charpy V-Notch (CVN) testing machine, cyclic immersion corrosion tester, XRD, optical microscopy (OM), scanning electron microscopy (SEM), and electron probe micro-analyzer (EPMA). The results showed that significant differences existed in the tensile strength, yield strength and impact toughness between HPS and PCS. After 72 h cyclic immersion accelerated corrosion test, the inner rust layer on HPS was composed of α-FeOOH phase and denser than that on PCS that was a mixture of α-FeOOH and Fe3O4. The rust formed on HPS provides better protection and HPS has lower corrosion rates than PCS. Copper and chromium in HPS enrich in the rust layer and enhance the compactness of the rust layer. Based on the results of the accelerated corrosion tests and rust layer analysis, the roles of Cu and Cr against corrosion are discussed, providing HPS with chemical specification which has been industrially successful to produce weathering steel for bridge structure.
关键词:
HPS
,
corrosion resistance
,
microstructure
,
mechanical property
M Yousefieh
,
M Shamanian
,
A Saatchi
钢铁研究学报(英文版)
The high corrosion resistance of duplex stainless steel (DSS) is due to elements such as Cr, Mo and N, but also depends on the microstructure. The best general properties are obtained with approximately equal amounts of austenite and ferrite and the absence of third phases such as σ (sigma) and Cr2N. In the present work the effect of heat input variations on the microstructure and corrosion resistance of a DSS UNS S32760 in artificial sea water media were studied. The corrosion resistance in 3.5% of NaCl solution was evaluated by potentiostatic polarization tests at room temperature. It is found that the presence of sigma phase and Cr2N decreases the corrosion potential. The specimen with heat input of approximately 0.95 kJ/mm have the best corrosion characteristics, which is the result for the lack of deleterious phases such as sigma and Cr2N and balanced ferrite-austenite proportion.
关键词:
steel
,
microstructure
,
corrosion
,
heat input
,
pulse current GTAW
Fatih Hayat
钢铁研究学报(英文版)
Zinc coated dual phase 600 steel (DP 600 grade) was investigated, utilisation of which has gradually increased with each passing day in the automotive industry. The adhesive bonding (AB), resistance spot welding (RSW), and adhesive weld bonding (AWB) joints of the zinc coated DP 600 steel were investigated. Additionally, the zinc coating was removed using HCL acid in order to investigate the effect of the coating. The microstructure, tensile shear strengths, and fracture properties of adhesive bonding (AB), resistance spot welding (RSW), and adhesive weld bonding (AWB) joints of the coated and uncoated DP 600 steel were compared. In addition, a mechanical-electrical-thermal coupled model in a finite element analysis environment was utilised. The thermal profile phenomenon was calculated by simulating this process. The results of the tensile shear test indicated that the tensile load bearing capacity (TLBC) values of the coated specimens among the three welding methods were higher than those of the uncoated specimens. Additionally, the tensile strength of the AWB joints of the coated and uncoated specimens was higher than that of the AB and RSW joints. It was determined that the fracture behaviours and the deformation caused were different for the three welding methods.
关键词:
advanced high strength steel
,
DP600
,
adhesive weld bonding
,
microstructure
,
deformation
,
fracture
HU Zheng-fei
,
WANG Qi-jiang
,
ZHANG Bin
钢铁研究学报(英文版)
Standardarized creep and rupture strength tests were conducted for commercial T91 martensitic heat-resistant steel at 650 ℃ and corresponding microstructure was characterized by BSED, TEM and EDS. The martensitic microstructure degenerated seriously during creep exposure, including martensitic substructure recovering, carbides coarsening, dissolving and precipitating. EDS analysis shows that the M23C6 carbides in different morphologies have dissimilar compositions. The rod/sheet like M23C6 particles within the matrix contain more additions, which might precipitate in situ while fine MX particles were re-solving. The high content of silicon in these rod/sheet like M23C6 carbides is probably related to self diffusion coefficient increasing for the exposed condition at 650 ℃ close to Curie temperature Tc. For those reasons, martensite substructure becomes unstable, and microstructure evolution is accelerated and leads to creep strength deteriorating severely.
关键词:
T91 steel
,
creep strength
,
microstructure
,
carbide
,
coarsening
,
self-diffusion
LI Yu-feng
,
LA Pei-qing
,
WEI Yu-peng
,
LU Yang
,
YANG Yang
钢铁研究学报(英文版)
Bulk nanocrystalline Fe3Al materials containing manganese of 10% were prepared by aluminothermic reaction. Hot pressing of those materials was performed at different temperatures and times. The microstructures of the alloy were investigated by optical microscope (OM) and electron probe microanalyzer (EPMA). The grain sizes of the materials were analyzed by X-ray diffraction (XRD) and transmission electron microscope (TEM). The results showed that the grain sizes of the materials increase after hot pressing. The grain sizes of the materials decrease with increasing the hot pressing times at the same temperature and the grain sizes of the materials increase with increasing hot pressing temperatures at identical times. The hardness and compressibility of the materials were also tested. The results showed that the hardness decreases with increasing hot pressing times at 800 ℃ and hardness increases with increasing the hot pressing temperatures. The variation of hardness with grain size of the nanocrystalline Fe3Al materials after hot pressing is contrary to the Hall-Petch relation. The materials are not broken during hot pressing and exhibit good plasticity and compressibility.
关键词:
hot pressing
,
Fe3Al nanostructure material
,
microstructure
,
mechanical property
ZHOU Min
,
DU Lin-xiu
,
LIU Xiang-hua
钢铁研究学报(英文版)
The variation of heat treatments including directed quenching and tempering off-line after controlled rolling (DQT) and quenching off-line and tempering off-line after controlled rolling (RQT) with microstructure and mechanical properties of a low-carbon microalloyed steel was compared and analyzed. For DQT, the quenched steel was obviously banded microstructure, with increasing tempering temperature, lath martensite coarsened, the cusp carbide precipitated at grain boundaries, the yield strength fluctuated slightly, and the fracture-separation was obvious. The impact toughness was better in the steel tempered at 500 ℃ for 1 h. In RQT, with increasing tempering temperature, lath martensite degenerated, intragranular and intergranular finer precipitations with smaller than 30 nm precipitated and grew up and were distributed dispersedly, the stripe-like carbides were distributed at grain boundaries, and the yield strength and tensile strengthen decreased obviously. The impact toughness of RQT process was much better than that of DQT process, and the comprehensive mechanical properties were better for the steel tempered at 500 ℃ for 1 h of RQT process.
关键词:
X120 pipeline steel
,
heat treatment
,
microstructure
,
mechanical property
,
fracture-separation
YANG Gang
,
YANG Mu-xin
,
LIU Zheng-dong
,
WANG Chang
钢铁研究学报(英文版)
Commercial pure iron billets having diameter of 60 mm and length of 180 mm were subjected to equal channel angular pressing (ECAP) at 350 ℃ for 1 to 4 passes via route Bc. Microstructural evolutions on three planes (X, Y, Z planes) were characterized by optical microscopy and transmission electron microscopy (TEM). It was found that after four passes an ultrafine microstructure could be formed on the X plane, but a band structure remained on the Z plane. Accordingly, the mechanical properties exhibited apparent dependence on the orientations. The strength in the x and y directions was higher than that in the z direction. The microstructural refinement and mechanical properties were discussed in terms of experimental results.
关键词:
iron
,
ECAP
,
UFG
,
microstructure
,
mechanical property
HAN Qihang
,
KANG Yonglin
,
ZHAO Xianmeng
,
L Chao
,
GAO Lufeng
钢铁研究学报(英文版)
Two kinds of ultrahigh strength cold rolled dual phase steels have been developed by designing CSiMnCr and CSiMnCrMo alloy systems. Tensile strength and elongation of both steels exceed 1100 MPa and 10%, respectively. The microstructures of both steels consist of massive martensite and ferrite. And the massive martensite of Mofree steel disperses in the ferrite with volume fraction of 64%. However, the massive martensite of Mocontaining steel is connected or closed by small martensite islands each other, and martensite volume fraction is 69%. As to Mofree steel, the yield strength, yield ratio, and work hardening exponent n are 548 MPa, 049, and 026, respectively. As for Mocontaining one, the yield strength, yield ratio, and n value are 746 MPa, 066, and 033, respectively. Besides, the ferrite of Mofree steel is deformed at the initial stage of plastic deformation. However, for Mocontaining one, Mo solution strengthened ferrite and small overaged martensite islands are deformed preferentially at small strain, which causes the yield strength to reach approximately 200 MPa higher than that of Mofree steel.
关键词:
Mo
,
dual phase steel
,
microstructure
,
property
,
deformation mechanism
ZHAO Jin-long
,
XI Yan
,
SHI Wen
,
LI Lin
钢铁研究学报(英文版)
Abstract： Microstructure evolution and mechanical properties of newly designed 01C-6Mn-05Si-1Al TRIP-aided steels under different annealing conditions and the effects of matrix microstructure before intercritical annealing on the final microstructure were studied by means of X-ray diffraction (XRD), scanning electron microcopy (SEM), dilatometric simulation, optical microstructure (OM) and tensile testing in this work. The experimental results indicate that the TRIP steel with Mn of 6% could form a considerable amount of retained austenite with good TRIP effect after a simple intercritical annealing treatment, and the matrix microstructure before intercritical annealing treatment can greatly affect the final microstructure. The original microstructure of the ferritic matrix steel was eliminated, while annealed martensite was remained from the martensite matrix steel under the same intercritical annealing conditions.
关键词:
Key words: high manganese TRIP steel
,
intercritical annealing
,
microstructure
,
mechanical properties
