Superplastic deformation of commercial OOCr22Ni5Mo3N0.17 duplex stainless steel

The superplastic behavior of a commercial duplex stainless steel has been studied by means of isothermal hot tensile test at temperatures of 850-1050? for the initial strain rates ranging from 3×10-4 s-1 to 5×10-2 s-1. At 960℃, the best superplastic deformation that caused the maximum elongation greater than 840% was obtained for an initial strain rate of 1.2×10-3 s-1. At 850℃, the best elongation 500% was achieved for an initial strain rate of 2.5×10-3 s-1. During the deformation in higher temperature region, coarse y grains formed during the prior treatments were broken into spherical particles, resulting in a homogeneous dispersion of y particles within the ?-ferrite matrix. However, at lower temperatures between 800 and 950℃, the o phase was formed through the eutectoid decomposition of ?-?+?, resulting finally in the stable equiaxed micro-duplex structures with δ/γ and γ/σ, respectively. The precipitation of the o phase played an important role in improving the superplasticity at 850℃.     

铸态0Cr17Mn14Mo2N双相不锈钢加热时元素的分配

研究了铸态双相不锈钢在高温加热时各元素在铁素体和奥氏体两相中的重新分配，结果表明：铬元素在两相中的分配比例受温度的影响不大，而钼元素在温度降低时倾向于分配到铁素体中，锰元素在温度升高时在奥氏体中的分布稍多一些。     

含稀土的23Cr型双相不锈钢的高温变形行为

利用Gleeble-3500热力模拟试验机在950-1200℃,应变速率为0.1-10s-1条件下进行了含稀土的23Cr型双相不锈钢的热压缩变形,获得了流变曲线,建立了热变形方程,分析了变形组织。结果表明：在流变曲线上既存在峰值应力也有稳态应力;在高温低应变速率条件下,峰值应变减小。上述变形条件下,试验钢的热变形激活能Q=436kJ/mol,表观应力指数n=3.91,热变形方程为：ε=2.41×1016[sinh（0.012σs）]3.91exp （-436000/RT）。奥氏体的动态再结晶在试验钢的动态软化机制中起主导作用且随着温度的升高和应变速率的降低越来越充分;而大应变下,铁素体的软化主要表现为较充分的动态回复。稀土元素影响了热变形时两相中Mo元素的再分配是稀土改善双相不锈钢高温塑性的重要原因之一。稀土使Mo在铁素体中浓度较低温度下降低,高温下升高;而奥氏体相中,使得Mo浓度在较低温度下升高而高温下降低。     

镍对07Cr17Ni12Mo2N奥氏体不锈钢组织和高温拉伸性能的影响

利用Gleeble-1500D热模拟机对07Cr17Ni12Mo2N奥氏体不锈钢试样分别在950,1000,1 050,1 100℃以0.05 s-1的应变速率进行了高温拉伸试验,通过分析试验钢组织、断面收缩率曲线、抗拉强度曲线、断口形貌,研究镍对试验钢高温拉伸性能的影响.结果表明：降镍后试验钢仍为单一的奥氏体组织;热塑性有所降低,断面收缩率平均下降了18.87％;抗拉强度平均提高了12.39％.     

Hot deformation behavior of microstructural constituents in a duplex stainless steel during high-temperature straining

The hot deformation characteristics of 1.4462 duplex stainless steel （DSS） were analyzed by considering strain partitioning between austenite and ferrite constituents. The individual behavior of ferrite and austenite in microstructure was studied in an iso-stress condition. Hot compression tests were performed at temperatures of 800-1100~C and strain rates of 0.001-1 s-1. The flow stress was modeled by a hyperbolic sine constitutive equation, the corresponding constants and apparent activation energies were determined for the studied alloys. The constitutive equation and law of mixture were used to measure the contribution factor of each phase at any given strain. It is found that the contribution factor of ferrite exponentially declines as the Zener-HoUomon parameter （Z） increases. On the contrary, the austenite contribution polynomially increases with the increase of Z. At low Z values below 2.6. x 1015 （lnZ---35.5）, a negative contribution factor is determined for austenite that is attributed to dynamic recrystallization. At high Z values, the contribution factor of austenite is about two orders of magnitude greater than that of ferrite, and therefore, austenite can accommodate more strain. Microstructural characterization via electron back-scattered diffraction （EBSD） confirms the mechanical results and shows that austenite recrystallization is possible only at high temperature and low strain rate.     

节镍奥氏体不锈钢Cr18Mn6Ni4N的组织及性能

为节约镍资源,研究了不同成分17.8~19.1%Cr,3.93~6.05%Mn,3.58~4.62%Ni,0.32~0.42%N节镍型奥氏体不锈钢固溶后的力学性能和耐蚀性能,以期获得可替代304不锈钢的新钢种。结果表明:Cr18.4Mn5.98Ni4.62N0.42不锈钢的力学性能和耐蚀性能与304不锈钢相当。分析了该成分不锈钢时效处理后的组织演变规律、冷变形过程中奥氏体稳定性及形变诱发马氏体相变过程。结果表明:800℃是Cr2N相析出的鼻尖温度,随着时效时间的增加,析出相首先以颗粒状形貌沿晶界析出,而后以胞状析出方式向晶内生长。冷轧压下率18.5%时尚未发现形变诱发马氏体组织,随着变形量增大,片层状ε'马氏体含量先增加后减少至消失,而板条状α'马氏体含量逐渐增多,相对磁导率增加,但其奥氏体稳定性远高于304不锈钢。可见,Cr18.4Mn5.98Ni4.62N0.42不锈钢可替代304不锈钢。     

离心机用0Cr18Ni9不锈钢腐蚀失效分析

螺旋卸料沉降式离心机具有连续进料、螺旋推进、高速运转等特点.卧式螺旋卸料沉降式离心机已经在农业、化工、轻工等部门广泛应用.作为离心式分离设备,其高速旋转的转鼓能产生极大的离心力,以完成各种物料的液-固及液-液分离.作为核心部件的转鼓必须满足3个条件：耐腐蚀、高强度及低能耗.只有三者兼备,才能保证离心机的使用性和安全性.同时,为保证焊接区域的整体性和使用的稳定性,应使用合理的焊材和焊接工艺.     

Microstructural developments and precipitate transformation during transient liquid-phase bonding of a duplex stainless steel

Effect of holding time on microstructural developments and transformation of precipitates formed at the interface during transient liquid-phase bonding of a duplex stainless steel using a Ni-based amorphous insert alloy was studied. The experimental results reveal that the microstructure of the adjacent base metal varies clearly as a function of holding time. The migration of Cr and Ni elements and the → transformation seem to play relevant roles in this microstructure evolution. The scanning electron microscopy (SEM) and electron prob X-ray microanalysis (EPMA) results indicate the transformation of BN→BN and (N, Mo) boride→BN at the interface with the holding time of 60-1 800 s. N content changes with holding time increasing at locations at the interface might be a controlling factor contributing to this transformation.     

Electrochemical corrosion behavior of the laser continuous heat treatment welded joints of 2205 duplex stainless steel

The electrochemical corrosion behaviors of the welded joints of 2205 duplex stainless steel with the laser continuous heat treatment were investigated. The secondary austenite formation is the outcome of thermodynamic equilibrium breach of the alloy during heat treatment and the result of the continuous heat treatment which has the most important effect on the weld material. The partitioning behaviors of chromium and molybdenum as well as the volume fraction of ferrite and austenite have a remarkable influence on the composition of the individual phase. Mechanical examination of the laser trated weld demonstrates that the tensile strength and yield strength increase with increasing the amount of the secondary austenite. It is shown that the ultimate tensile strength of the 6 kW laser-treated weld is higher about 20 MPa than no heat treatment weld and the ductility can be further improved without compromising strength. The results indicate that the welding alters the corrosion behavior because of different post heat treatment power and the broad active peak is not identified which is attributed to the dissolution of the secondary austenitic in the ferrite phase. It is indicated that pitting resistance equivalent (PRE) values of base metal and 6 kW weld are higher than that of other welds; base metal is 33.7, 6 kW weld 33.3, no treatment 32.4, 4 kW weld 32.8, 8 kW weld 32.5. The extent of corrosion resistance improvement after reheating treatment is mainly caused by the removal of nitrogen from ferritic regions, which occurred as a consequence of secondary austenite growth.     

0Cr18Ni9不锈钢焊接温度场的数值仿真

基于有限元软件SYSWELD对不锈钢0Cr18Ni9平板TIG焊的温度场进行三维动态模拟,得出了瞬态温度场分布图和特征点的热循环曲线,同时也得出了焊缝上任一点的温度变化与相变的关系.与文献资料比较表明,所建立的数值模拟仿真模型可以较好的模拟焊接温度场,为研究焊接过程中的应力应变和减少焊接应力与变形提供了参考依据.     

Determination of plastic equation of state by indentation method on 304 stainless steel

An indentation method for determining the plastic mechanical equation of state (PES) was studied. The constant loading rate and constant loading rate/load indentation tests were carried out. The method for determining the work-hardening coefficient and the strain rate sensitivity coefficient of PES were discussed in detail. 304 stainless steel hot-treated at 1100℃ was used to verify the method. The work-hardening coefficient and strain rate sensitivity coefficient of 304 stainless steel were respectively determined as 0.30 and 0.015. These values are very close to those achieved by tensile tests. From the establishment of the PES of 304 stainless steel it is shown that the PES obtained by the indentation method is easier than that by the tensile test.     

40Mn26Al3Cr6Re 奥氏体不锈钢复合钝化膜的TEM研究

对铁－锰－铝－铬奥氏体不锈钢４０Ｍｎ２６Ａｌ３Ｃｒ６Ｒｅ在０．５ｍｏｌ／ＬＨ２ＳＯ４溶液中钝化后形成的表面膜进行了ＴＥＭ分析研究．ＴＥＭ分析结果证明：４０Ｍｎ２６Ａｌ３Ｃｒ６Ｒｅ不锈钢表面钝化膜主要是α－Ａｌ２Ｏ３、θ－Ａｌ２Ｏ３、（Ｃｒ２Ｏ３）１０Ｂ的机械混合物；其中（Ｃｒ２Ｏ３）１０Ｂ的含量最多．钝化膜为层状结构，内层为多晶，外层是微晶和非晶；钝化膜与基体在结晶学上存在外延关系．     

含稀土元素Y的2Cr13不锈钢热变形组织与性能研究

利用Cleeble-1500D热模拟试验机,研究含稀土元素Y的2Cr13不锈钢热变形性能及冷却后组织.通过观察分析原始组织与四道次变形后组织,以及热模拟试验曲线,得出了四道次变形后的组织和应力应变的变化规律.     

Simulation of dynamic recrystallization in 23Co13Ni11Cr3Mo steel using a modified cellular automaton简

A modified cellular automaton（CA） program was developed to simulate the process of dynamic recrystallization（DRX） for 23Co13Ni11Cr3Mo ultrahigh strength steel.In this model,influences of deformation parameters on hardening rate and solute drag effect were considered.Moreover,an inverse analysis method was proposed for parameters identification of dislocation model and solute drag effect based on the results of isothermal compression tests on Gleeble-1500.Then,simulated microstructures under different deformation conditions were compared with those of experiments.A good agreement is achieved.Furthermore,influences of deformation parameters on microstructure evolution for 23Co13Ni11Cr3Mo steel were investigated in details.High strain is an effective measure to refine grain and improve homogeneity.Meanwhile,the desired deformation parameters are temperature of 1000-1050 °C and strain rate of 0.008-0.01 s-1 for obtaining grains smaller than 22.5 μm.     

Effect of anions on stress corrosion cracking behaviors of ultra-high strength steel 23Co14Ni12Cr3Mo

The effects of chloride, sulfate and carbonate anions on stress corrosion behaviors of ultra-high strength steel 23Co14Ni12Cr3Mo were studied by stress corrosion cracking （SCC） test method using double cantilever beam （DCB） specimens. The SCC morphology was observed by using scanning electron microscopy （SEM） and the composition of corrosion products was analyzed by using energy dispersive spectrometer （EDS）. The results show that the crack propagates to bifurcation in NaCl and Na2SO4 solution, while the crack in Na2CO3 solution propagates along the load direction. The SCC rate in NaCl solution is the highest, while lower in Na2SO4 solution and little in Na2CO3 solution. From the SEM morphologies, quasi-cleavage fracture was observed in NaCl and Na2SO4 solutions, but intergranular features in Na2CO3 solution. The mechanism of anion effect on SCC of steel 23Co14Ni12Cr3Mo was studied by using full immersion test and electrochemical measurements.