节镍无磁不锈钢Cr18Ni6Mn3N的组织及性能

研究了节镍无磁不锈钢Cr18Ni6Mn3N的热轧及固溶后的力学性能和耐蚀性能,分析了其固溶和时效析出后的组织演变规律、冷变形过程中形变诱发马氏体相变及其磁性能.结果表明:该不锈钢的固溶组织为单相奥氏体,其力学性能和耐蚀性能均高于SUS304不锈钢;800℃保温4 h后,在晶界析出粒状氮化物,随着保温时间延长,逐渐沿晶界凸起片层状析出物并向晶内生长,保温20 h后,凸出的片层状析出物直径达20μm.冷轧压下率18.3%时尚未发现形变诱发马氏体组织,随着变形量增大,马氏体含量增多,磁导率上升,但与相同条件下的SUS304不锈钢相比,冷轧板固溶后相对磁导率可降至1.002,因此可用于低成本无磁不锈钢领域.     

水下和陆上送丝式激光沉积铝合金的微观组织和显微硬度

铝合金因其比强度高、耐腐蚀性能好而被广泛应用于船舶和核电等领域。然而,由于服役环境恶劣,铝合金易于发生腐蚀失效。与传统修复方法相比,水下送丝式激光沉积具有受水压影响小、自动化程度高等优点。目前,对于薄壁管状结构铝合金的表面修复研究较少,尤其是水环境下的原位表面修复。本文首次在薄壁管状结构铝合金的表面进行了水下原位送丝式激光沉积,并与陆上送丝式激光沉积进行了对比分析。水下和陆上沉积层均成形良好,不存在未熔合、裂纹等缺陷。与陆上沉积层相比,水下沉积层的氧化程度略重。在水下和陆上沉积层的熔化区中,柱状晶均在熔合线处形核,并沿最大冷却速率方向生长;在沉积区中均形成了等轴晶。随着激光沉积环境从陆上转变为水下,沉积区宽度和熔化区高度均减小,而沉积角和沉积区高度均增大。由于水环境中激光沉积过程的冷却速率较大,使得峰值温度较低且高温停留时间较短,导致水下激光沉积的晶粒尺寸较小,大角度晶界所占比例较低。此外,水下沉积区的镁元素含量高于陆上的,表明水环境的存在有利于降低沉积区中镁元素烧损。水下沉积层的平均显微硬度高于陆上的,这主要与晶粒尺寸和镁元素烧损有关,根据Hall–Petch公式,材料的晶粒尺寸越细小,显微硬度越高;另外,镁元素含量较高,有利于提高铝-镁合金的显微硬度。     

Cr—Mn合金渗碳钢锻件正火处理后的显微组织和性能

研究了两种Cr-Mn合金渗碳钢锻件的普通正火和等温正火工艺参数对显微组织和性能的影响，得出普通正火较难获得技术要求的显微组织和性能，等温正火则容易满足技术要求。     

H型钢热轧过程微观组织的数值预报

将热力耦合有限元方法与金属微观组织演变数学模型相结合,提出了热变形过程微观组织的数值预报方法。作为应用,模拟了Ｈ型钢热轧过程的微观组织演变。预报值与实测值吻合良好,表明本文方法己能成功预报热变形后的金属微观组织。     

时效处理对17-7PH不锈钢微观组织和维氏硬度的影响

采用JSM-6480扫描电子显微镜（scanning electron microscope,SEM）、Wilson Tukon 1102维氏硬度计研究了时效处理对17-7PH不锈钢微观组织和维氏硬度的影响。结果表明：17-7PH不锈钢经过0 ℃/30 min深冷处理后,在560 ℃进行时效处理,随着时效时间的延长,维氏硬度逐渐降低,未进行时效处理时的维氏硬度最高,为481;-73 ℃/8 h深冷处理后,再510 ℃/30 min时效处理,达到峰值时效硬度,维氏硬度为500,继续延长时效时间,维氏硬度逐渐降低。     

异步轧制AZ31镁合金板材组织

对不同总变形量、道次压下量、轧制温度以及轧制路径等工艺条件下所制备的AZ31镁合金板材的组织进行研究。研究结果表明：异步轧制有利于板材的晶粒细化,其晶粒粒度约为8．9μm,明显小于常规轧制板材的13．2μm;当总变形量由40％增大到80％时,晶粒粒度从40μm左右减小到30μm左右,出现了较多的孪晶;当道次压下量由5％增加到20％时,晶粒粒度从40μm左右减小到10～20μm,孪晶数量也随之减少;当温度由350℃升高到400℃时,晶粒粒度由20μm左右下降到10μm,且大部分晶粒为等轴晶;轧制路径的改变,使板材中的显微组织和孪晶数量产生改变,C路径中的晶粒细小,粒度约为10μm,D路径中的孪晶数量最少。     

热处理工艺对T8钢显微组织及硬度的影响

T8钢由于含碳量高,过剩碳化物极多,塑性和韧性差,若热处理工艺不合适,使材料在服役早期出现开裂和破碎的现象。通过SEM,OPM及XRD等试验方法,研究了T8钢组织和性能随球化退火时间、淬火温度及回火温度的变化。结果表明：T8钢在600℃球化退火2 h后,原始组织中的碳化物即可获得充分球化,以粒状形式细小均匀地分布在基体中,延长退火时间不显著改变碳化物的球化效果;试样经（770±10）℃保温,6 min油淬后,获得的隐晶马氏体组织硬度最高;试样经180~210℃回火1 h空冷后,消除了淬火过程中产生的残余应力,最终获得有球状碳化物均匀分布的隐晶马氏体组织,回火试样硬度较淬火态略有下降。     

喷射沉积H13钢的组织和硬度

用传统铸造和喷射成形工艺制备了H13钢,然后再进行锻造加工,利用光学金相显微镜(OM)、扫描电子显微镜(SEM)、X射线衍射分析(XRD)等分析方法及硬度测试对不同工艺制备的H13钢的显微组织和硬度进行分析.研究结果表明,喷射成形及其锻造加工的H13钢的组织及硬度明显的优于传统工艺制备的H13钢.     

18Mn18Cr高氮钢析出相特征及形成机制

通过金相显微镜、扫描电镜、电子探针显微分析、透射电镜及热力学计算软件研究C和N含量对铸态及时效态18Mn18Cr高氮钢析出相特征及形成机制的影响.研究发现在铸态,随C/N质量比降低,析出相依次为Cr23C6相、σ相和Cr2N相.增加C或N含量可分别促进Cr23C6相和Cr2N相析出.C和N含量影响实验钢凝固模式及不稳定铁素体相共析分解产物.18Mn18Cr0.44N钢凝固模式为AF模式,不稳定铁素体相共析分解反应为δ→σ+γ2(0.025%C)和δ→γ2+Cr23(CxNy)6(x/y>1)(0.16%C);18Mn18Cr0.72N钢凝固模式为A模式,晶界处存在少量颗粒状Cr2N相.在固溶时效态,实验钢仅析出片层状的Cr2N0.39C0.61相.随C+N含量增加,片层状析出相体积分数和片层间隙增加,析出孕育时间减少.     

Cr元素对Al-Ni合金凝固组织及显微硬度的影响

采用光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDS)、X射线衍射分析(XRD)和硬度测试等手段研究Cr元素对Al-Ni合金的相组成、凝固组织及显微硬度的影响。结果表明,AlNi2.5Crx合金凝固组织主要为α(Al)相和共晶组织Al-Al_3Ni;Cr的添加细化了合金凝固组织,当Cr的原子分数为0.2%时,α(Al)细化效果最佳,当Cr的原子分数为0.3%时,Al_3Ni细化效果最佳;随着Cr含量的增加,合金硬度得到提高,当Cr的原子分数为0.5%时,合金硬度达到最大值51.2HV,这是固溶强化、细晶强化和晶格畸变共同作用的结果。     

Fe-18Mn-10Al-0.6C的热变形行为

热变形行为的研究对材料动态再结晶发生的判断以及热加工工艺参数的制定具有很重要的理论参考价值。对Fe-Mn-Al-C钢进行单道次压缩变形实验,利用Gleeble-3500热模拟试验机完成,变形温度为1 123~1 373 K,应变速率为0.01,0.1,1,10 s-1,测定真应力-真应变曲线,结合变形组织分析不同变形条件对动态再结晶的影响,建立热变形本构方程。结果表明:变形温度越高,应变速率越低,越有利于动态再结晶的进行;实验用钢的热变形激活能和表观应力指数分别为343.351 k J/mol和4.683,本构方程为ε=3.926 2×10~(13)[sinh(0.006σ)]~(4.6830)exp(-343.35/8.314T)     

18-18-0.5N高氮奥氏体不锈钢冷轧变形过程中的组织演变和形变强化

利用XRD、TEM、SEM和拉伸实验等分析测试方法研究了18-18-0.5N高氮奥氏体不锈钢在冷轧变形过程中的组织演变和形变强化规律.结果发现:18-18-0.5N高氮奥氏体不锈钢在冷变形过程中并未发生形变诱导相变,微观组织和力学性能在变形量为43.8%附近出现转折.提出了屈服强度随应变变化的预测方程.     

Influence of hot rolling on the microstructure of lean duplex stainless steel 2101

In this work, the microstructure and the strain partitioning of lean duplex stainless steel 2101 (LDX 2101) during different hot-rolling processes are investigated by optical microscopy and electron-backscattered diffraction (EBSD). The results show that the LDX 2101 exhibits poor thermoplasticity at high temperature. The four-pass hot-rolled plates show fewer edge-cracking defects and superior thermoplasticity compared with the two-pass hot-rolled plates prepared at different temperature. The phase boundary is the weakest site in the LDX 2101. The cracks are initiated and propagated along the phase boundaries during the hot-rolling process. According to the EBSD analysis, the increase of the hot-rolling pass can dramatically improve the strain distribution in ferrite and austenite phases and promote the strain transmission in the constituent phases, thereby improving the coordinated deformation ability of the two phases. This effect further increases the thermoplasticity and reduces the formation of edge cracks in LDX 2101.     

带钢热连轧非对称因素对板形的影响

为研究某2250 mm热连轧生产中非对称因素对轧件非对称板形(如楔形和单边浪)的影响,利用基于影响函数法的辊系变形模型、张应力模型和简化的轧制压力横向分布模型相结合的方法,建立了集轧机和轧件为一体的非对称板形计算模型。研究结果表明：来料楔形对轧件楔形的影响明显超过其对轧件平坦度的影响;上游机架和下游机架刚度非对称分别主要影响轧件楔形和平坦度;40益以内的轧件温度不对称分布对轧件平坦度影响较小,对出口楔形的影响可以忽略;轧件跑偏对楔形和平坦度均有显著影响。根据板形良好条件确定了各非对称参数的允许范围。     

热等静压316L不锈钢致密体的组织与性能

采用热等静压方法对气雾化316L奥氏体不锈钢粉末致密化,用箱式电阻炉对致密体进行了固溶处理,研究了固溶前后致密体的显微组织和力学性能,并对其拉伸断口形貌进行了分析．结果表明：热等静压态致密体密度接近理论全致密,内部组织为细小的奥氏体,存在较多的碳化物,抗拉强度、屈服强度分别达到595．3MPa和263．3MPa,延伸率为58．3％,硬度为HBS152．3;固溶处理使致密体强度和硬度降低,塑性增加,且随着固溶温度的提高,强度迅速降低,塑性明显提高,最佳固溶温度为1050℃;在固溶温度为1050℃和水冷的情况下,最佳保温时间为20min;固溶处理前后拉伸试样断口呈现明显的韧性断裂,固溶韧性好于固溶前的,均高于热轧态产品的韧性．     

Test research on sticking mechanism during hot rolling of SUS 430 ferritic stainless steel

The sticking phenomenon during hot rolling of SUS 430 ferritic stainless steel was investigated by means of a two-disc type high-temperature wear tester. The test results indicate that sticking particles on the surfaces of high chromium steel (HiCr) and high-speed steel (HSS) rolls undergo nucleation, growth, and saturation stages. Grooves on the roll surface generated by grinding provide nucleation sites for sticking particles. The number of sticking particles on the HiCr roll surface is greater than that on the HSS roll surface. The average surface roughnesses (R_a) of HiCr and HSS rolls change from 0.502 and 0.493 μm at the initial stage to 0.837 and 0.530 μm at the saturation stage, respectively. The test further proves that the sticking behavior is strongly dependent on roll materials, and the HSS roll is more beneficial to prevent particles sticking compared with the HiCr roll under the same hot-rolling conditions.     

Semi-solid slurry preparation and rolling of 1Cr18Ni9Ti stainless steel

The preparation and rolling of the semi-solid slurry 1Cr18Ni9Ti stainless steel were researched. The experimental results show that when stirred for 2-3 min under the given test condition, the semi-solid slurry with about 50%-60% (volume fraction) solid and the spherical primary austenitic grains in the size of 100-200 μm can be obtained, and it is easy to be discharged from the bottom little hole of the stirring chamber. The semi-solid slurry of 1Cr18Ni9Ti stainless steel can be rolled into the given plate successfully.However, the solid phase and liquid phase are easily separated in the rolling process, so that the solid primary austenitic grains are concentrated in the center and the liquid phase is near the edge of the rolled plate. The strengths of the plate rolled in the semi-solid state are higher than that of the traditionally repeated hot-rolled plate of 1Cr18Ni9Ti stainless steel.     

Effects of asymmetric rolling process on ridging resistance of ultra-purified 17%Cr ferritic stainless steel

In ferritic stainless steels, a significant non-uniform recrystallization orientation and a substantial texture gradient usually occur, which can degrade the ridging resistance of the final sheets. To improve the homogeneity of the recrystallization orientation and reduce the texture gradient in ultra-purified 17%Cr ferritic stainless steel, in this work, we performed conventional and asymmetric rolling processes and conducted macro and micro-texture analyses to investigate texture evolution under different cold-rolling conditions. In the conventional rolling specimens, we observed that the deformation was not uniform in the thickness direction, whereas there was homogeneous shear deformation in the asymmetric rolling specimens as well as the formation of uniform recrystallized grains and random orientation grains in the final annealing sheets. As such, the ridging resistance of the final sheets was significantly improved by employing the asymmetric rolling process. This result indicates with certainty that the texture gradient and orientation inhomogeneity can be attributed to non-uniform deformation, whereas the uniform orientation gradient in the thickness direction is explained by the increased number of shear bands obtained in the asymmetric rolling process.     

非对称热轧高品质不锈钢复合板可行性模拟研究

利用特厚规格复合板与较薄规格复合板进行非对称组坯,采用ABAQUS有限元软件对其热轧过程中的应变、接触应力及温度分布进行计算,并通过温度补偿及冷却控制的手段,对热轧非对称复合坯的可行性进行模拟分析。结果表明,采用非对称组坯设计,有利于特厚复合板碳钢层与不锈钢层在各道次轧制中的界面结合;通过控制复合坯上、下表面的温差,能有效改善板坯翘曲现象,并可一次性获得一块宽幅特厚复合板与一块宽幅较薄规格复合板,提高生产效率;此外,采用非对称组坯设计还可实现控轧控冷,保证芯部不锈钢与碳钢的协同变形,促进其界面结合。     

Static and dynamic finite element analysis of 304 stainless steel rod and wire hot continuous rolling process

Three-dimensional finite element models were developed to analyze 304 stainless steel rod and wire hot continuous rolling process with the help of MSC.Marc software. The entire 30-pass deformation process and the actual parameters of production line were taken into account. Static and dynamic procedures were used to study the continuous rolling process with the aid of the thermo-mechanical coupled FEM of elastic-plasticity. The properties of billets, such as deformation, temperature field and rolling force, were mainly discussed. The simulation results of temperature agree well with the measured values. Comparisons of the analysis results obtained using static implicit method and dynamic implicit method were presented. It is shown that static implicit procedure is more accurate than dynamic implicit procedure and is able to simulate the rolling process with a lower speed, such as a roughing mill. Whereas, dynamic analysis shows a higher efficiency than static analysis and is fit for simulating the rolling process with a higher speed, such as a finishing mill.